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class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#description">Description</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#constructor">Constructor</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#static_properties">Static properties</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#instance_properties">Instance properties</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#instance_methods">Instance methods</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#examples">Examples</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#specifications">Specifications</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#browser_compatibility">Browser compatibility</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#see_also">See also</a></li> </ul> </section> </div> </div> <div class="sidebar-body"> <ol> <li class="section"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">Standard built-in objects</a></li> <li class="section"><em><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB" aria-current="page"><code>SharedArrayBuffer</code></a></em></li> <li> <details open> <summary>Constructor</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer() constructor</code></a></li> </ol> </details></li> <li> <details open> <summary>Static properties</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/Symbol.species?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer[Symbol.species]</code></a></li> </ol> </details></li> <li> <details open> <summary>Instance methods</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/grow?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer.prototype.grow()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/slice?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer.prototype.slice()</code></a></li> </ol> </details></li> <li> <details open> <summary>Instance properties</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/byteLength?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer.prototype.byteLength</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/growable?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer.prototype.growable</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/maxByteLength?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer.prototype.maxByteLength</code></a></li> </ol> </details></li> <li class="section no-link">Inheritance</li> <li class="section"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object/Function</code></a></li> <li> <details> <summary>Static methods</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/apply?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function.prototype.apply()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function.prototype.bind()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function.prototype.call()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/Symbol.hasInstance?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function.prototype[Symbol.hasInstance]()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/toString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function.prototype.toString()</code></a></li> </ol> </details></li> <li> <details> <summary>Static properties</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/arguments?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function.prototype.arguments</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/caller?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function.prototype.caller</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/displayName?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function: displayName</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/length?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function: length</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/name?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function: name</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/prototype?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Function: prototype</code></a></li> </ol> </details></li> <li> <details> <summary>Instance methods</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineGetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__defineGetter__()</code></a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineSetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__defineSetter__()</code></a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupGetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__lookupGetter__()</code></a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupSetter__?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__lookupSetter__()</code></a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.hasOwnProperty()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isPrototypeOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.isPrototypeOf()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.propertyIsEnumerable()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toLocaleString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.toLocaleString()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.toString()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.valueOf()</code></a></li> </ol> </details></li> <li> <details> <summary>Instance properties</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.constructor</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.__proto__</code></a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li> </ol> </details></li> </ol> </div> </div> <section class="place side"></section> </nav> </aside> <div class="toc-container"> <aside class="toc"> <nav> <div class="document-toc-container"> <section class="document-toc"> <header> <h2 class="document-toc-heading">In this article</h2> </header> <ul class="document-toc-list"> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#description">Description</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#constructor">Constructor</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#static_properties">Static properties</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#instance_properties">Instance properties</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#instance_methods">Instance methods</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#examples">Examples</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#specifications">Specifications</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#browser_compatibility">Browser compatibility</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#see_also">See also</a></li> </ul> </section> </div> </nav> </aside> <section class="place side"></section> </div> </div> <main id="content" class="main-content "> <article class="main-page-content" lang="en-US"> <header> <h1>SharedArrayBuffer</h1> <details class="baseline-indicator high"> <summary><span class="indicator" role="img" aria-label="Baseline Check"></span><h2>Baseline <span class="not-bold">Widely available</span></h2> <div class="browsers"> <span class="engine" title="Supported in Chrome and Edge"><span class="browser chrome supported" role="img" aria-label="Chrome check"></span><span class="browser edge supported" role="img" aria-label="Edge check"></span></span><span class="engine" title="Supported in Firefox"><span class="browser firefox supported" role="img" aria-label="Firefox check"></span></span><span class="engine" title="Supported in Safari"><span class="browser safari supported" role="img" aria-label="Safari check"></span></span> </div><span class="icon icon-chevron "></span></summary> <div class="extra"> <p>This feature is well established and works across many devices and browser versions. It’s been available across browsers since December 2021.</p> <ul> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Glossary/Baseline/Compatibility?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB" data-glean="baseline_link_learn_more" target="_blank" class="learn-more">Learn more</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#browser_compatibility" data-glean="baseline_link_bcd_table">See full compatibility</a></li> <li><a href="https://translate.google.com/website?sl=pl&tl=tr&hl=en-GB&u=https://survey.alchemer.com/s3/7634825/MDN-baseline-feedback?page%3D%252Fen-US%252Fdocs%252FWeb%252FJavaScript%252FReference%252FGlobal_Objects%252FSharedArrayBuffer%26level%3Dhigh" data-glean="baseline_link_feedback" class="feedback-link" target="_blank" rel="noreferrer">Report feedback</a></li> </ul> </div> </details> </header> <div class="section-content"> <p>The <strong><code>SharedArrayBuffer</code></strong> object is used to represent a generic raw binary data buffer, similar to the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>ArrayBuffer</code></a> object, but in a way that they can be used to create views on shared memory. A <code>SharedArrayBuffer</code> is not a <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/API/Web_Workers_API/Transferable_objects?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">Transferable Object</a>, unlike an <code>ArrayBuffer</code> which is transferable.</p> </div> <section aria-labelledby="description"> <h2 id="description"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#description">Description</a></h2> <div class="section-content"> <p>To share memory using <code>SharedArrayBuffer</code> objects from one agent in the cluster to another (an agent is either the web page's main program or one of its web workers), <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/API/Worker/postMessage?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>postMessage</code></a> and <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">structured cloning</a> is used.</p> <p>The structured clone algorithm accepts <code>SharedArrayBuffer</code> objects and typed arrays mapped onto <code>SharedArrayBuffer</code> objects. In both cases, the <code>SharedArrayBuffer</code> object is transmitted to the receiver resulting in a new, private <code>SharedArrayBuffer</code> object in the receiving agent (just as for <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>ArrayBuffer</code></a>). However, the shared data block referenced by the two <code>SharedArrayBuffer</code> objects is the same data block, and a side effect to the block in one agent will eventually become visible in the other agent.</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const sab = new SharedArrayBuffer(1024); worker.postMessage(sab); </code></pre> </div> <p>Shared memory can be created and updated simultaneously in workers or the main thread. Depending on the system (the CPU, the OS, the Browser) it can take a while until the change is propagated to all contexts. To synchronize, <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Atomics?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">atomic</a> operations are needed.</p> <p><code>SharedArrayBuffer</code> objects are used by some web APIs, such as:</p> <ul> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/API/WebGLRenderingContext/bufferData?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>WebGLRenderingContext.bufferData()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/API/WebGLRenderingContext/bufferSubData?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>WebGLRenderingContext.bufferSubData()</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/API/WebGL2RenderingContext/getBufferSubData?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>WebGL2RenderingContext.getBufferSubData()</code></a></li> </ul> </div> </section> <section aria-labelledby="security_requirements"> <h3 id="security_requirements"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#security_requirements">Security requirements</a></h3> <div class="section-content"> <p>Shared memory and high-resolution timers were effectively <a href="https://translate.google.com/website?sl=pl&tl=tr&hl=en-GB&u=https://blog.mozilla.org/security/2018/01/03/mitigations-landing-new-class-timing-attack/" class="external" target="_blank">disabled at the start of 2018</a> in light of <a href="https://translate.google.com/website?sl=pl&tl=tr&hl=en-GB&u=https://en.wikipedia.org/wiki/Spectre_(security_vulnerability)" class="external" target="_blank">Spectre</a>. In 2020, a new, secure approach has been standardized to re-enable shared memory.</p> <p>As a baseline requirement, your document needs to be in a <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/Security/Secure_Contexts?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">secure context</a>.</p> <p>For top-level documents, two headers need to be set to cross-origin isolate your site:</p> <ul> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/HTTP/Headers/Cross-Origin-Opener-Policy?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Cross-Origin-Opener-Policy</code></a> with <code>same-origin</code> as value (protects your origin from attackers)</li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/HTTP/Headers/Cross-Origin-Embedder-Policy?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Cross-Origin-Embedder-Policy</code></a> with <code>require-corp</code> or <code>credentialless</code> as value (protects victims from your origin)</li> </ul> <div class="code-example"> <div class="example-header"> <span class="language-name">http</span> </div> <pre class="brush: http notranslate"><code>Cross-Origin-Opener-Policy: same-origin Cross-Origin-Embedder-Policy: require-corp </code></pre> </div> <p>To check if cross origin isolation has been successful, you can test against the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/API/Window/crossOriginIsolated?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Window.crossOriginIsolated</code></a> property or the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/API/WorkerGlobalScope/crossOriginIsolated?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>WorkerGlobalScope.crossOriginIsolated</code></a> property available to window and worker contexts:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const myWorker = new Worker("worker.js"); if (crossOriginIsolated) { const buffer = new SharedArrayBuffer(16); myWorker.postMessage(buffer); } else { const buffer = new ArrayBuffer(16); myWorker.postMessage(buffer); } </code></pre> </div> <p>With these two headers set, <code>postMessage()</code> no longer throws for <code>SharedArrayBuffer</code> objects and shared memory across threads is therefore available.</p> <p>Nested documents and dedicated workers need to set the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/HTTP/Headers/Cross-Origin-Embedder-Policy?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Cross-Origin-Embedder-Policy</code></a> header as well, with the same value. No further changes are needed for same-origin nested documents and subresources. Same-site (but cross-origin) nested documents and subresources need to set the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/HTTP/Headers/Cross-Origin-Resource-Policy?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Cross-Origin-Resource-Policy</code></a> header with <code>same-site</code> as value. And their cross-origin (and cross-site) counterparts need to set the same header with <code>cross-origin</code> as value. Note that setting the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/HTTP/Headers/Cross-Origin-Resource-Policy?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Cross-Origin-Resource-Policy</code></a> header to any other value than <code>same-origin</code> opens up the resource to potential attacks, such as <a href="https://translate.google.com/website?sl=pl&tl=tr&hl=en-GB&u=https://en.wikipedia.org/wiki/Spectre_(security_vulnerability)" class="external" target="_blank">Spectre</a>.</p> <p>Note that the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/HTTP/Headers/Cross-Origin-Opener-Policy?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Cross-Origin-Opener-Policy</code></a> header limits your ability to retain a reference to popups. Direct access between two top-level window contexts essentially only work if they are same-origin and carry the same two headers with the same two values.</p> </div> </section> <section aria-labelledby="api_availability"> <h3 id="api_availability"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#api_availability">API availability</a></h3> <div class="section-content"> <p>Depending on whether the above security measures are taken, the various memory-sharing APIs have different availabilities:</p> <ul> <li>The <code>Atomics</code> object is always available.</li> <li><code>SharedArrayBuffer</code> objects are in principle always available, but unfortunately the constructor on the global object is hidden, unless the two headers mentioned above are set, for compatibility with web content. There is hope that this restriction can be removed in the future. <a href="https://developer-mozilla-org.translate.goog/en-US/docs/WebAssembly/JavaScript_interface/Memory?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>WebAssembly.Memory</code></a> can still be used to get an instance.</li> <li>Unless the two headers mentioned above are set, the various <code>postMessage()</code> APIs will throw for <code>SharedArrayBuffer</code> objects. If they are set, <code>postMessage()</code> on <code>Window</code> objects and dedicated workers will function and allow for memory sharing.</li> </ul> </div> </section> <section aria-labelledby="webassembly_shared_memory"> <h3 id="webassembly_shared_memory"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#webassembly_shared_memory">WebAssembly shared memory</a></h3> <div class="section-content"> <p><a href="https://developer-mozilla-org.translate.goog/en-US/docs/WebAssembly/JavaScript_interface/Memory?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>WebAssembly.Memory</code></a> objects can be created with the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/WebAssembly/JavaScript_interface/Memory/Memory?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#shared"><code>shared</code></a> constructor flag. When this flag is set to <code>true</code>, the constructed <code>Memory</code> object can be shared between workers via <code>postMessage()</code>, just like <code>SharedArrayBuffer</code>, and the backing <a href="https://developer-mozilla-org.translate.goog/en-US/docs/WebAssembly/JavaScript_interface/Memory/buffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>buffer</code></a> of the <code>Memory</code> object is a <code>SharedArrayBuffer</code>. Therefore, the requirements listed above for sharing a <code>SharedArrayBuffer</code> between workers also apply to sharing a <code>WebAssembly.Memory</code>.</p> <p>The WebAssembly Threads proposal also defines a new set of <a href="https://translate.google.com/website?sl=pl&tl=tr&hl=en-GB&u=https://github.com/WebAssembly/threads/blob/master/proposals/threads/Overview.md%23atomic-memory-accesses" class="external" target="_blank">atomic</a> instructions. Just as <code>SharedArrayBuffer</code> and its methods are unconditionally enabled (and only sharing between threads is gated on the new headers), the WebAssembly atomic instructions are also unconditionally allowed.</p> </div> </section> <section aria-labelledby="growing_sharedarraybuffers"> <h3 id="growing_sharedarraybuffers"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#growing_sharedarraybuffers">Growing SharedArrayBuffers</a></h3> <div class="section-content"> <p><code>SharedArrayBuffer</code> objects can be made growable by including the <code>maxByteLength</code> option when calling the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer()</code></a> constructor. You can query whether a <code>SharedArrayBuffer</code> is growable and what its maximum size is by accessing its <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/growable?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>growable</code></a> and <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/maxByteLength?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>maxByteLength</code></a> properties, respectively. You can assign a new size to a growable <code>SharedArrayBuffer</code> with a <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/grow?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>grow()</code></a> call. New bytes are initialized to 0.</p> <p>These features make growing <code>SharedArrayBuffer</code>s more efficient — otherwise, you have to make a copy of the buffer with a new size. It also gives JavaScript parity with WebAssembly in this regard (Wasm linear memory can be resized with <a href="https://developer-mozilla-org.translate.goog/en-US/docs/WebAssembly/JavaScript_interface/Memory/grow?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>WebAssembly.Memory.prototype.grow()</code></a>).</p> <p>For security reasons, <code>SharedArrayBuffer</code>s cannot be reduced in size, only grown.</p> </div> </section> <section aria-labelledby="constructor"> <h2 id="constructor"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#constructor">Constructor</a></h2> <div class="section-content"> <dl> <dt id="sharedarraybuffer"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer()</code></a> </dt> <dd> <p>Creates a new <code>SharedArrayBuffer</code> object.</p> </dd> </dl> </div> </section> <section aria-labelledby="static_properties"> <h2 id="static_properties"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#static_properties">Static properties</a></h2> <div class="section-content"> <dl> <dt id="sharedarraybuffersymbol.species"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/Symbol.species?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer[Symbol.species]</code></a> </dt> <dd> <p>Returns the constructor used to construct return values from <code>SharedArrayBuffer</code> methods.</p> </dd> </dl> </div> </section> <section aria-labelledby="instance_properties"> <h2 id="instance_properties"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#instance_properties">Instance properties</a></h2> <div class="section-content"> <p>These properties are defined on <code>SharedArrayBuffer.prototype</code> and shared by all <code>SharedArrayBuffer</code> instances.</p> <dl> <dt id="sharedarraybuffer.prototype.bytelength"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/byteLength?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer.prototype.byteLength</code></a> </dt> <dd> <p>The size, in bytes, of the array. This is established when the array is constructed and can only be changed using the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/grow?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer.prototype.grow()</code></a> method if the <code>SharedArrayBuffer</code> is growable.</p> </dd> <dt id="sharedarraybuffer.prototype.constructor"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer.prototype.constructor</code></a> </dt> <dd> <p>The constructor function that created the instance object. For <code>SharedArrayBuffer</code> instances, the initial value is the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer</code></a> constructor.</p> </dd> <dt id="sharedarraybuffer.prototype.growable"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/growable?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer.prototype.growable</code></a> </dt> <dd> <p>Read-only. Returns <code>true</code> if the <code>SharedArrayBuffer</code> can be grown, or <code>false</code> if not.</p> </dd> <dt id="sharedarraybuffer.prototype.maxbytelength"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/maxByteLength?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer.prototype.maxByteLength</code></a> </dt> <dd> <p>The read-only maximum length, in bytes, that the <code>SharedArrayBuffer</code> can be grown to. This is established when the array is constructed and cannot be changed.</p> </dd> <dt id="sharedarraybuffer.prototypesymbol.tostringtag"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#sharedarraybuffer.prototypesymbol.tostringtag"><code>SharedArrayBuffer.prototype[Symbol.toStringTag]</code></a> </dt> <dd> <p>The initial value of the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/toStringTag?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>[Symbol.toStringTag]</code></a> property is the string <code>"SharedArrayBuffer"</code>. This property is used in <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Object.prototype.toString()</code></a>.</p> </dd> </dl> </div> </section> <section aria-labelledby="instance_methods"> <h2 id="instance_methods"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#instance_methods">Instance methods</a></h2> <div class="section-content"> <dl> <dt id="sharedarraybuffer.prototype.grow"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/grow?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer.prototype.grow()</code></a> </dt> <dd> <p>Grows the <code>SharedArrayBuffer</code> to the specified size, in bytes.</p> </dd> <dt id="sharedarraybuffer.prototype.slice"> <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/slice?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>SharedArrayBuffer.prototype.slice()</code></a> </dt> <dd> <p>Returns a new <code>SharedArrayBuffer</code> whose contents are a copy of this <code>SharedArrayBuffer</code>'s bytes from <code>begin</code>, inclusive, up to <code>end</code>, exclusive. If either <code>begin</code> or <code>end</code> is negative, it refers to an index from the end of the array, as opposed to from the beginning.</p> </dd> </dl> </div> </section> <section aria-labelledby="examples"> <h2 id="examples"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#examples">Examples</a></h2> <div class="section-content"></div> </section> <section aria-labelledby="creating_a_new_sharedarraybuffer"> <h3 id="creating_a_new_sharedarraybuffer"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#creating_a_new_sharedarraybuffer">Creating a new SharedArrayBuffer</a></h3> <div class="section-content"> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const sab = new SharedArrayBuffer(1024); </code></pre> </div> </div> </section> <section aria-labelledby="slicing_the_sharedarraybuffer"> <h3 id="slicing_the_sharedarraybuffer"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#slicing_the_sharedarraybuffer">Slicing the SharedArrayBuffer</a></h3> <div class="section-content"> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>sab.slice(); // SharedArrayBuffer { byteLength: 1024 } sab.slice(2); // SharedArrayBuffer { byteLength: 1022 } sab.slice(-2); // SharedArrayBuffer { byteLength: 2 } sab.slice(0, 1); // SharedArrayBuffer { byteLength: 1 } </code></pre> </div> </div> </section> <section aria-labelledby="using_it_in_a_webgl_buffer"> <h3 id="using_it_in_a_webgl_buffer"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#using_it_in_a_webgl_buffer">Using it in a WebGL buffer</a></h3> <div class="section-content"> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const canvas = document.querySelector("canvas"); const gl = canvas.getContext("webgl"); const buffer = gl.createBuffer(); gl.bindBuffer(gl.ARRAY_BUFFER, buffer); gl.bufferData(gl.ARRAY_BUFFER, sab, gl.STATIC_DRAW); </code></pre> </div> </div> </section> <h2 id="specifications"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#specifications">Specifications</a></h2> <table class="standard-table"> <thead> <tr> <th scope="col">Specification</th> </tr> </thead> <tbody> <tr> <td><a href="https://translate.google.com/website?sl=pl&tl=tr&hl=en-GB&u=https://tc39.es/ecma262/multipage/structured-data.html%23sec-sharedarraybuffer-objects">ECMAScript Language Specification <br><small># sec-sharedarraybuffer-objects</small></a></td> </tr> </tbody> </table> <h2 id="browser_compatibility"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#browser_compatibility">Browser compatibility</a></h2> <p>BCD tables only load in the browser <noscript>with JavaScript enabled. Enable JavaScript to view data. </noscript></p> <section aria-labelledby="see_also"> <h2 id="see_also"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB#see_also">See also</a></h2> <div class="section-content"> <ul> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Atomics?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Atomics</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>ArrayBuffer</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Guide/Typed_arrays?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">JavaScript typed arrays</a> guide</li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/API/Web_Workers_API?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">Web Workers</a></li> <li><a href="https://translate.google.com/website?sl=pl&tl=tr&hl=en-GB&u=https://github.com/tc39/proposal-ecmascript-sharedmem/blob/main/TUTORIAL.md" class="external" target="_blank">Shared Memory – a brief tutorial</a> in the TC39 ecmascript-sharedmem proposal</li> <li><a href="https://translate.google.com/website?sl=pl&tl=tr&hl=en-GB&u=https://hacks.mozilla.org/2016/05/a-taste-of-javascripts-new-parallel-primitives/" class="external" target="_blank">A Taste of JavaScript's New Parallel Primitives</a> on hacks.mozilla.org (2016)</li> <li><a href="https://translate.google.com/website?sl=pl&tl=tr&hl=en-GB&u=https://docs.google.com/document/d/1zDlfvfTJ_9e8Jdc8ehuV4zMEu9ySMCiTGMS9y0GU92k/edit" class="external" target="_blank">COOP and COEP explained</a> by the Chrome team (2020)</li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/HTTP/Headers/Cross-Origin-Opener-Policy?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Cross-Origin-Opener-Policy</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/HTTP/Headers/Cross-Origin-Embedder-Policy?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Cross-Origin-Embedder-Policy</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/HTTP/Headers/Cross-Origin-Resource-Policy?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Cross-Origin-Resource-Policy</code></a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/API/Window/crossOriginIsolated?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>Window.crossOriginIsolated</code></a> and <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/API/WorkerGlobalScope/crossOriginIsolated?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB"><code>WorkerGlobalScope.crossOriginIsolated</code></a></li> <li><a href="https://translate.google.com/website?sl=pl&tl=tr&hl=en-GB&u=https://developer.chrome.com/blog/enabling-shared-array-buffer/" class="external" target="_blank">SharedArrayBuffer updates in Android Chrome 88 and Desktop Chrome 92</a> on developer.chrome.com (2021)</li> </ul> </div> </section> </article> <aside class="article-footer"> <div class="article-footer-inner"> <div class="svg-container"> <svg xmlns="http://www.w3.org/2000/svg" width="162" height="162" viewbox="0 0 162 162" fill="none" role="none"> <mask id="b" fill="#fff"> <path d="M97.203 47.04c8.113-7.886 18.004-13.871 28.906-17.492a78 78 0 0 1 33.969-3.39c11.443 1.39 22.401 5.295 32.024 11.411s17.656 14.28 23.476 23.86c5.819 9.579 9.269 20.318 10.083 31.385a69.85 69.85 0 0 1-5.387 32.44c-4.358 10.272-11.115 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Content available under <a href="https://developer-mozilla-org.translate.goog/en-US/docs/MDN/Writing_guidelines/Attrib_copyright_license?_x_tr_sl=pl&_x_tr_tl=tr&_x_tr_hl=en-GB">a Creative Commons license</a>.</p> </div> </div> </footer> </div> <script type="application/json" id="hydration">{"url":"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer","doc":{"isMarkdown":true,"isTranslated":false,"isActive":true,"flaws":{},"title":"SharedArrayBuffer","mdn_url":"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer","locale":"en-US","native":"English (US)","browserCompat":["javascript.builtins.SharedArrayBuffer"],"baseline":{"baseline":"high","baseline_high_date":"2024-06-13","baseline_low_date":"2021-12-13","support":{"chrome":"68","chrome_android":"89","edge":"79","firefox":"79","firefox_android":"79","safari":"15.2","safari_ios":"15.2"}},"sidebarHTML":"<ol><li class=\"section\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects\">Standard built-in objects</a></li><li class=\"section\"><em><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer\" aria-current=\"page\"><code>SharedArrayBuffer</code></a></em></li><li><details open=\"\"><summary>Constructor</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/SharedArrayBuffer\"><code>SharedArrayBuffer() constructor</code></a></li></ol></details></li><li><details open=\"\"><summary>Static properties</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/Symbol.species\"><code>SharedArrayBuffer[Symbol.species]</code></a></li></ol></details></li><li><details open=\"\"><summary>Instance methods</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/grow\"><code>SharedArrayBuffer.prototype.grow()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/slice\"><code>SharedArrayBuffer.prototype.slice()</code></a></li></ol></details></li><li><details open=\"\"><summary>Instance properties</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/byteLength\"><code>SharedArrayBuffer.prototype.byteLength</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/growable\"><code>SharedArrayBuffer.prototype.growable</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/maxByteLength\"><code>SharedArrayBuffer.prototype.maxByteLength</code></a></li></ol></details></li><li class=\"section no-link\">Inheritance</li><li class=\"section\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object\"><code>Object/Function</code></a></li><li><details><summary>Static methods</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/apply\"><code>Function.prototype.apply()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind\"><code>Function.prototype.bind()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call\"><code>Function.prototype.call()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/Symbol.hasInstance\"><code>Function.prototype[Symbol.hasInstance]()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/toString\"><code>Function.prototype.toString()</code></a></li></ol></details></li><li><details><summary>Static properties</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/arguments\"><code>Function.prototype.arguments</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/caller\"><code>Function.prototype.caller</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/displayName\"><code>Function: displayName</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/length\"><code>Function: length</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/name\"><code>Function: name</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/prototype\"><code>Function: prototype</code></a></li></ol></details></li><li><details><summary>Instance methods</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineGetter__\"><code>Object.prototype.__defineGetter__()</code></a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineSetter__\"><code>Object.prototype.__defineSetter__()</code></a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupGetter__\"><code>Object.prototype.__lookupGetter__()</code></a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupSetter__\"><code>Object.prototype.__lookupSetter__()</code></a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty\"><code>Object.prototype.hasOwnProperty()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isPrototypeOf\"><code>Object.prototype.isPrototypeOf()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable\"><code>Object.prototype.propertyIsEnumerable()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toLocaleString\"><code>Object.prototype.toLocaleString()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString\"><code>Object.prototype.toString()</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf\"><code>Object.prototype.valueOf()</code></a></li></ol></details></li><li><details><summary>Instance properties</summary><ol><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor\"><code>Object.prototype.constructor</code></a></li><li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto\"><code>Object.prototype.__proto__</code></a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li></ol></details></li></ol>","sidebarMacro":"JSRef","body":[{"type":"prose","value":{"id":null,"title":null,"isH3":false,"content":"<p>The <strong><code>SharedArrayBuffer</code></strong> object is used to represent a generic raw binary data buffer, similar to the <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer\"><code>ArrayBuffer</code></a> object, but in a way that they can be used to create views on shared memory. A <code>SharedArrayBuffer</code> is not a <a href=\"/en-US/docs/Web/API/Web_Workers_API/Transferable_objects\">Transferable Object</a>, unlike an <code>ArrayBuffer</code> which is transferable.</p>"}},{"type":"prose","value":{"id":"description","title":"Description","isH3":false,"content":"<p>To share memory using <code>SharedArrayBuffer</code> objects from one agent in the cluster to another (an agent is either the web page's main program or one of its web workers), <a href=\"/en-US/docs/Web/API/Worker/postMessage\"><code>postMessage</code></a> and <a href=\"/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm\">structured cloning</a> is used.</p>\n<p>The structured clone algorithm accepts <code>SharedArrayBuffer</code> objects and typed arrays mapped onto <code>SharedArrayBuffer</code> objects. In both cases, the <code>SharedArrayBuffer</code> object is transmitted to the receiver resulting in a new, private <code>SharedArrayBuffer</code> object in the receiving agent (just as for <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer\"><code>ArrayBuffer</code></a>). However, the shared data block referenced by the two <code>SharedArrayBuffer</code> objects is the same data block, and a side effect to the block in one agent will eventually become visible in the other agent.</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const sab = new SharedArrayBuffer(1024);\nworker.postMessage(sab);\n</code></pre></div>\n<p>Shared memory can be created and updated simultaneously in workers or the main thread. Depending on the system (the CPU, the OS, the Browser) it can take a while until the change is propagated to all contexts. To synchronize, <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Atomics\">atomic</a> operations are needed.</p>\n<p><code>SharedArrayBuffer</code> objects are used by some web APIs, such as:</p>\n<ul>\n <li><a href=\"/en-US/docs/Web/API/WebGLRenderingContext/bufferData\"><code>WebGLRenderingContext.bufferData()</code></a></li>\n <li><a href=\"/en-US/docs/Web/API/WebGLRenderingContext/bufferSubData\"><code>WebGLRenderingContext.bufferSubData()</code></a></li>\n <li><a href=\"/en-US/docs/Web/API/WebGL2RenderingContext/getBufferSubData\"><code>WebGL2RenderingContext.getBufferSubData()</code></a></li>\n</ul>"}},{"type":"prose","value":{"id":"security_requirements","title":"Security requirements","isH3":true,"content":"<p>Shared memory and high-resolution timers were effectively <a href=\"https://blog.mozilla.org/security/2018/01/03/mitigations-landing-new-class-timing-attack/\" class=\"external\" target=\"_blank\">disabled at the start of 2018</a> in light of <a href=\"https://en.wikipedia.org/wiki/Spectre_(security_vulnerability)\" class=\"external\" target=\"_blank\">Spectre</a>. In 2020, a new, secure approach has been standardized to re-enable shared memory.</p>\n<p>As a baseline requirement, your document needs to be in a <a href=\"/en-US/docs/Web/Security/Secure_Contexts\">secure context</a>.</p>\n<p>For top-level documents, two headers need to be set to cross-origin isolate your site:</p>\n<ul>\n <li><a href=\"/en-US/docs/Web/HTTP/Headers/Cross-Origin-Opener-Policy\"><code>Cross-Origin-Opener-Policy</code></a> with <code>same-origin</code> as value (protects your origin from attackers)</li>\n <li><a href=\"/en-US/docs/Web/HTTP/Headers/Cross-Origin-Embedder-Policy\"><code>Cross-Origin-Embedder-Policy</code></a> with <code>require-corp</code> or <code>credentialless</code> as value (protects victims from your origin)</li>\n</ul>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">http</span></div><pre class=\"brush: http notranslate\"><code>Cross-Origin-Opener-Policy: same-origin\nCross-Origin-Embedder-Policy: require-corp\n</code></pre></div>\n<p>To check if cross origin isolation has been successful, you can test against the <a href=\"/en-US/docs/Web/API/Window/crossOriginIsolated\"><code>Window.crossOriginIsolated</code></a> property or the <a href=\"/en-US/docs/Web/API/WorkerGlobalScope/crossOriginIsolated\"><code>WorkerGlobalScope.crossOriginIsolated</code></a> property available to window and worker contexts:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const myWorker = new Worker(\"worker.js\");\n\nif (crossOriginIsolated) {\n const buffer = new SharedArrayBuffer(16);\n myWorker.postMessage(buffer);\n} else {\n const buffer = new ArrayBuffer(16);\n myWorker.postMessage(buffer);\n}\n</code></pre></div>\n<p>With these two headers set, <code>postMessage()</code> no longer throws for <code>SharedArrayBuffer</code> objects and shared memory across threads is therefore available.</p>\n<p>Nested documents and dedicated workers need to set the <a href=\"/en-US/docs/Web/HTTP/Headers/Cross-Origin-Embedder-Policy\"><code>Cross-Origin-Embedder-Policy</code></a> header as well, with the same value. No further changes are needed for same-origin nested documents and subresources. Same-site (but cross-origin) nested documents and subresources need to set the <a href=\"/en-US/docs/Web/HTTP/Headers/Cross-Origin-Resource-Policy\"><code>Cross-Origin-Resource-Policy</code></a> header with <code>same-site</code> as value. And their cross-origin (and cross-site) counterparts need to set the same header with <code>cross-origin</code> as value. Note that setting the <a href=\"/en-US/docs/Web/HTTP/Headers/Cross-Origin-Resource-Policy\"><code>Cross-Origin-Resource-Policy</code></a> header to any other value than <code>same-origin</code> opens up the resource to potential attacks, such as <a href=\"https://en.wikipedia.org/wiki/Spectre_(security_vulnerability)\" class=\"external\" target=\"_blank\">Spectre</a>.</p>\n<p>Note that the <a href=\"/en-US/docs/Web/HTTP/Headers/Cross-Origin-Opener-Policy\"><code>Cross-Origin-Opener-Policy</code></a> header limits your ability to retain a reference to popups. Direct access between two top-level window contexts essentially only work if they are same-origin and carry the same two headers with the same two values.</p>"}},{"type":"prose","value":{"id":"api_availability","title":"API availability","isH3":true,"content":"<p>Depending on whether the above security measures are taken, the various memory-sharing APIs have different availabilities:</p>\n<ul>\n <li>The <code>Atomics</code> object is always available.</li>\n <li><code>SharedArrayBuffer</code> objects are in principle always available, but unfortunately the constructor on the global object is hidden, unless the two headers mentioned above are set, for compatibility with web content. There is hope that this restriction can be removed in the future. <a href=\"/en-US/docs/WebAssembly/JavaScript_interface/Memory\"><code>WebAssembly.Memory</code></a> can still be used to get an instance.</li>\n <li>Unless the two headers mentioned above are set, the various <code>postMessage()</code> APIs will throw for <code>SharedArrayBuffer</code> objects. If they are set, <code>postMessage()</code> on <code>Window</code> objects and dedicated workers will function and allow for memory sharing.</li>\n</ul>"}},{"type":"prose","value":{"id":"webassembly_shared_memory","title":"WebAssembly shared memory","isH3":true,"content":"<p><a href=\"/en-US/docs/WebAssembly/JavaScript_interface/Memory\"><code>WebAssembly.Memory</code></a> objects can be created with the <a href=\"/en-US/docs/WebAssembly/JavaScript_interface/Memory/Memory#shared\"><code>shared</code></a> constructor flag. When this flag is set to <code>true</code>, the constructed <code>Memory</code> object can be shared between workers via <code>postMessage()</code>, just like <code>SharedArrayBuffer</code>, and the backing <a href=\"/en-US/docs/WebAssembly/JavaScript_interface/Memory/buffer\"><code>buffer</code></a> of the <code>Memory</code> object is a <code>SharedArrayBuffer</code>. Therefore, the requirements listed above for sharing a <code>SharedArrayBuffer</code> between workers also apply to sharing a <code>WebAssembly.Memory</code>.</p>\n<p>The WebAssembly Threads proposal also defines a new set of <a href=\"https://github.com/WebAssembly/threads/blob/master/proposals/threads/Overview.md#atomic-memory-accesses\" class=\"external\" target=\"_blank\">atomic</a> instructions. Just as <code>SharedArrayBuffer</code> and its methods are unconditionally enabled (and only sharing between threads is gated on the new headers), the WebAssembly atomic instructions are also unconditionally allowed.</p>"}},{"type":"prose","value":{"id":"growing_sharedarraybuffers","title":"Growing SharedArrayBuffers","isH3":true,"content":"<p><code>SharedArrayBuffer</code> objects can be made growable by including the <code>maxByteLength</code> option when calling the <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/SharedArrayBuffer\"><code>SharedArrayBuffer()</code></a> constructor. You can query whether a <code>SharedArrayBuffer</code> is growable and what its maximum size is by accessing its <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/growable\"><code>growable</code></a> and <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/maxByteLength\"><code>maxByteLength</code></a> properties, respectively. You can assign a new size to a growable <code>SharedArrayBuffer</code> with a <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/grow\"><code>grow()</code></a> call. New bytes are initialized to 0.</p>\n<p>These features make growing <code>SharedArrayBuffer</code>s more efficient — otherwise, you have to make a copy of the buffer with a new size. It also gives JavaScript parity with WebAssembly in this regard (Wasm linear memory can be resized with <a href=\"/en-US/docs/WebAssembly/JavaScript_interface/Memory/grow\"><code>WebAssembly.Memory.prototype.grow()</code></a>).</p>\n<p>For security reasons, <code>SharedArrayBuffer</code>s cannot be reduced in size, only grown.</p>"}},{"type":"prose","value":{"id":"constructor","title":"Constructor","isH3":false,"content":"<dl>\n <dt id=\"sharedarraybuffer\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/SharedArrayBuffer\"><code>SharedArrayBuffer()</code></a></dt>\n <dd>\n <p>Creates a new <code>SharedArrayBuffer</code> object.</p>\n </dd>\n</dl>"}},{"type":"prose","value":{"id":"static_properties","title":"Static properties","isH3":false,"content":"<dl>\n <dt id=\"sharedarraybuffersymbol.species\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/Symbol.species\"><code>SharedArrayBuffer[Symbol.species]</code></a></dt>\n <dd>\n <p>Returns the constructor used to construct return values from <code>SharedArrayBuffer</code> methods.</p>\n </dd>\n</dl>"}},{"type":"prose","value":{"id":"instance_properties","title":"Instance properties","isH3":false,"content":"<p>These properties are defined on <code>SharedArrayBuffer.prototype</code> and shared by all <code>SharedArrayBuffer</code> instances.</p>\n<dl>\n <dt id=\"sharedarraybuffer.prototype.bytelength\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/byteLength\"><code>SharedArrayBuffer.prototype.byteLength</code></a></dt>\n <dd>\n <p>The size, in bytes, of the array. This is established when the array is constructed and can only be changed using the <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/grow\"><code>SharedArrayBuffer.prototype.grow()</code></a> method if the <code>SharedArrayBuffer</code> is growable.</p>\n </dd>\n <dt id=\"sharedarraybuffer.prototype.constructor\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor\"><code>SharedArrayBuffer.prototype.constructor</code></a></dt>\n <dd>\n <p>The constructor function that created the instance object. For <code>SharedArrayBuffer</code> instances, the initial value is the <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/SharedArrayBuffer\"><code>SharedArrayBuffer</code></a> constructor.</p>\n </dd>\n <dt id=\"sharedarraybuffer.prototype.growable\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/growable\"><code>SharedArrayBuffer.prototype.growable</code></a></dt>\n <dd>\n <p>Read-only. Returns <code>true</code> if the <code>SharedArrayBuffer</code> can be grown, or <code>false</code> if not.</p>\n </dd>\n <dt id=\"sharedarraybuffer.prototype.maxbytelength\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/maxByteLength\"><code>SharedArrayBuffer.prototype.maxByteLength</code></a></dt>\n <dd>\n <p>The read-only maximum length, in bytes, that the <code>SharedArrayBuffer</code> can be grown to. This is established when the array is constructed and cannot be changed.</p>\n </dd>\n <dt id=\"sharedarraybuffer.prototypesymbol.tostringtag\"><a href=\"#sharedarraybuffer.prototypesymbol.tostringtag\"><code>SharedArrayBuffer.prototype[Symbol.toStringTag]</code></a></dt>\n <dd>\n <p>The initial value of the <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/toStringTag\"><code>[Symbol.toStringTag]</code></a> property is the string <code>\"SharedArrayBuffer\"</code>. This property is used in <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString\"><code>Object.prototype.toString()</code></a>.</p>\n </dd>\n</dl>"}},{"type":"prose","value":{"id":"instance_methods","title":"Instance methods","isH3":false,"content":"<dl>\n <dt id=\"sharedarraybuffer.prototype.grow\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/grow\"><code>SharedArrayBuffer.prototype.grow()</code></a></dt>\n <dd>\n <p>Grows the <code>SharedArrayBuffer</code> to the specified size, in bytes.</p>\n </dd>\n <dt id=\"sharedarraybuffer.prototype.slice\"><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/slice\"><code>SharedArrayBuffer.prototype.slice()</code></a></dt>\n <dd>\n <p>Returns a new <code>SharedArrayBuffer</code> whose contents are a copy of this <code>SharedArrayBuffer</code>'s bytes from <code>begin</code>, inclusive, up to <code>end</code>, exclusive. If either <code>begin</code> or <code>end</code> is negative, it refers to an index from the end of the array, as opposed to from the beginning.</p>\n </dd>\n</dl>"}},{"type":"prose","value":{"id":"examples","title":"Examples","isH3":false,"content":""}},{"type":"prose","value":{"id":"creating_a_new_sharedarraybuffer","title":"Creating a new SharedArrayBuffer","isH3":true,"content":"<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const sab = new SharedArrayBuffer(1024);\n</code></pre></div>"}},{"type":"prose","value":{"id":"slicing_the_sharedarraybuffer","title":"Slicing the SharedArrayBuffer","isH3":true,"content":"<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>sab.slice(); // SharedArrayBuffer { byteLength: 1024 }\nsab.slice(2); // SharedArrayBuffer { byteLength: 1022 }\nsab.slice(-2); // SharedArrayBuffer { byteLength: 2 }\nsab.slice(0, 1); // SharedArrayBuffer { byteLength: 1 }\n</code></pre></div>"}},{"type":"prose","value":{"id":"using_it_in_a_webgl_buffer","title":"Using it in a WebGL buffer","isH3":true,"content":"<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const canvas = document.querySelector(\"canvas\");\nconst gl = canvas.getContext(\"webgl\");\nconst buffer = gl.createBuffer();\ngl.bindBuffer(gl.ARRAY_BUFFER, buffer);\ngl.bufferData(gl.ARRAY_BUFFER, sab, gl.STATIC_DRAW);\n</code></pre></div>"}},{"type":"specifications","value":{"title":"Specifications","id":"specifications","isH3":false,"specifications":[{"bcdSpecificationURL":"https://tc39.es/ecma262/multipage/structured-data.html#sec-sharedarraybuffer-objects","title":"ECMAScript Language Specification"}],"query":"javascript.builtins.SharedArrayBuffer"}},{"type":"browser_compatibility","value":{"title":"Browser compatibility","id":"browser_compatibility","isH3":false,"query":"javascript.builtins.SharedArrayBuffer"}},{"type":"prose","value":{"id":"see_also","title":"See also","isH3":false,"content":"<ul>\n <li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Atomics\"><code>Atomics</code></a></li>\n <li><a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer\"><code>ArrayBuffer</code></a></li>\n <li><a href=\"/en-US/docs/Web/JavaScript/Guide/Typed_arrays\">JavaScript typed arrays</a> guide</li>\n <li><a href=\"/en-US/docs/Web/API/Web_Workers_API\">Web Workers</a></li>\n <li><a href=\"https://github.com/tc39/proposal-ecmascript-sharedmem/blob/main/TUTORIAL.md\" class=\"external\" target=\"_blank\">Shared Memory – a brief tutorial</a> in the TC39 ecmascript-sharedmem proposal</li>\n <li><a href=\"https://hacks.mozilla.org/2016/05/a-taste-of-javascripts-new-parallel-primitives/\" class=\"external\" target=\"_blank\">A Taste of JavaScript's New Parallel Primitives</a> on hacks.mozilla.org (2016)</li>\n <li><a href=\"https://docs.google.com/document/d/1zDlfvfTJ_9e8Jdc8ehuV4zMEu9ySMCiTGMS9y0GU92k/edit\" class=\"external\" target=\"_blank\">COOP and COEP explained</a> by the Chrome team (2020)</li>\n <li><a href=\"/en-US/docs/Web/HTTP/Headers/Cross-Origin-Opener-Policy\"><code>Cross-Origin-Opener-Policy</code></a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Headers/Cross-Origin-Embedder-Policy\"><code>Cross-Origin-Embedder-Policy</code></a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Headers/Cross-Origin-Resource-Policy\"><code>Cross-Origin-Resource-Policy</code></a></li>\n <li><a href=\"/en-US/docs/Web/API/Window/crossOriginIsolated\"><code>Window.crossOriginIsolated</code></a> and <a href=\"/en-US/docs/Web/API/WorkerGlobalScope/crossOriginIsolated\"><code>WorkerGlobalScope.crossOriginIsolated</code></a></li>\n <li><a href=\"https://developer.chrome.com/blog/enabling-shared-array-buffer/\" class=\"external\" target=\"_blank\">SharedArrayBuffer updates in Android Chrome 88 and Desktop Chrome 92</a> on developer.chrome.com (2021)</li>\n</ul>"}}],"toc":[{"text":"Description","id":"description"},{"text":"Constructor","id":"constructor"},{"text":"Static properties","id":"static_properties"},{"text":"Instance properties","id":"instance_properties"},{"text":"Instance methods","id":"instance_methods"},{"text":"Examples","id":"examples"},{"text":"Specifications","id":"specifications"},{"text":"Browser compatibility","id":"browser_compatibility"},{"text":"See also","id":"see_also"}],"summary":"The SharedArrayBuffer object is used to represent a generic raw binary data buffer, similar to the ArrayBuffer object, but in a way that they can be used to create views on shared memory. A SharedArrayBuffer is not a Transferable Object, unlike an ArrayBuffer which is transferable.","popularity":0.0185,"modified":"2024-07-15T11:50:05.000Z","other_translations":[{"locale":"de","title":"SharedArrayBuffer","native":"Deutsch"},{"locale":"fr","title":"SharedArrayBuffer","native":"Français"},{"locale":"ja","title":"SharedArrayBuffer","native":"日本語"},{"locale":"ko","title":"SharedArrayBuffer","native":"한국어"},{"locale":"ru","title":"SharedArrayBuffer","native":"Русский"},{"locale":"zh-CN","title":"SharedArrayBuffer","native":"中文 (简体)"}],"pageType":"javascript-class","source":{"folder":"en-us/web/javascript/reference/global_objects/sharedarraybuffer","github_url":"https://github.com/mdn/content/blob/main/files/en-us/web/javascript/reference/global_objects/sharedarraybuffer/index.md","last_commit_url":"https://github.com/mdn/content/commit/6fbdb78c1362fae31fbd545f4b2d9c51987a6bca","filename":"index.md"},"short_title":"SharedArrayBuffer","parents":[{"uri":"/en-US/docs/Web","title":"References"},{"uri":"/en-US/docs/Web/JavaScript","title":"JavaScript"},{"uri":"/en-US/docs/Web/JavaScript/Reference","title":"Reference"},{"uri":"/en-US/docs/Web/JavaScript/Reference/Global_Objects","title":"Standard built-in objects"},{"uri":"/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer","title":"SharedArrayBuffer"}],"pageTitle":"SharedArrayBuffer - JavaScript | MDN","noIndexing":false}}</script> <script>function gtElInit() {var lib = new google.translate.TranslateService();lib.translatePage('pl', 'tr', function () {});}</script> <script src="https://translate.google.com/translate_a/element.js?cb=gtElInit&hl=en-GB&client=wt" type="text/javascript"></script> </body> </html>