CINXE.COM
Understanding Guideline 4.1: Compatible | WAI | W3C
<!DOCTYPE html><html lang="en" xml:lang="en" xmlns="http://www.w3.org/1999/xhtml"><head> <meta charset="UTF-8"> <title>Understanding Guideline 4.1: Compatible | WAI | W3C</title> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="stylesheet" href="https://w3.org/WAI/assets/css/style.css"> <link rel="stylesheet" href="base.css"> </head> <body dir="ltr"> <a href="#main" class="button button--skip-link">Skip to content</a> <div class="minimal-header-container default-grid"> <header class="minimal-header" id="site-header"> <div class="minimal-header-name"> <a href="https://www.w3.org/WAI/WCAG21/Understanding/">WCAG 2.1 Understanding Docs</a> </div> <div class="minimal-header-subtitle">Informative explanations, not required to meet WCAG</div> <a class="minimal-header-link" href="https://www.w3.org/WAI/WCAG21/Understanding/about">About WCAG Understanding Docs</a> <div class="minimal-header-logo"> <a href="http://w3.org/" aria-label="W3C"> <svg xmlns="http://www.w3.org/2000/svg" height="2em" viewBox="0 0 91.968 44"> <g fill-rule="evenodd" fill="none"> <path fill="#015a9c" d="M-.231-.21h92.917v44.659H-.23z"></path> <g fill-rule="nonzero" fill="#fff"> <path d="M21.752 0l7.789 26.78L37.329 0H58.444v2.662l-7.95 13.852c2.792.907 4.905 2.555 6.337 4.944 1.432 2.391 2.149 5.196 2.149 8.419 0 3.985-1.048 7.335-3.143 10.05C53.742 42.642 51.029 44 47.7 44c-2.507 0-4.691-.806-6.552-2.417-1.862-1.611-3.24-3.793-4.136-6.546l4.403-1.846c.646 1.666 1.496 2.979 2.552 3.938 1.056.96 2.3 1.438 3.733 1.438 1.504 0 2.775-.85 3.813-2.552 1.039-1.703 1.558-3.747 1.558-6.14 0-2.643-.556-4.69-1.664-6.138-1.29-1.701-3.314-2.554-6.071-2.554h-2.148v-2.606l7.52-13.147H41.63l-.516.889-11.04 37.678h-.536L21.48 16.73l-8.056 27.268h-.537L0 0h5.64l7.787 26.78 5.264-18.033L16.113 0zM87.958 0c-1.077 0-2.044.388-2.777 1.133-.777.79-1.21 1.81-1.21 2.866s.412 2.034 1.167 2.8C85.905 7.579 86.892 8 87.959 8c1.043 0 2.055-.422 2.843-1.188.755-.733 1.166-1.711 1.166-2.811a3.997 3.997 0 00-1.155-2.811A3.946 3.946 0 0087.958 0zm3.476 4.034a3.32 3.32 0 01-1.01 2.41c-.69.668-1.544 1.023-2.489 1.023a3.405 3.405 0 01-2.42-1.033c-.655-.667-1.022-1.523-1.022-2.433 0-.911.378-1.8 1.055-2.489.633-.645 1.488-.988 2.42-.988.955 0 1.81.356 2.477 1.033.645.643.99 1.51.99 2.477zm-3.366-2.378h-1.71v4.533h.855V4.256h.845l.922 1.933h.955l-1.012-2.066c.655-.134 1.033-.578 1.033-1.223 0-.822-.621-1.244-1.888-1.244zm-.155.555c.8 0 1.165.222 1.165.778 0 .533-.365.722-1.144.722h-.722v-1.5zM82.109 0l.862 5.914-3.05 6.588s-1.172-2.795-3.118-4.342c-1.64-1.303-2.708-1.586-4.378-1.198-2.145.5-4.577 3.394-5.638 6.963-1.27 4.27-1.283 6.336-1.328 8.234-.071 3.042.354 4.841.354 4.841s-1.853-3.868-1.835-9.533c.012-4.043.576-7.71 2.233-11.328 1.459-3.181 3.626-5.09 5.55-5.315 1.99-.232 3.562.85 4.777 2.02 1.276 1.23 2.565 3.918 2.565 3.918zM82.202 31.824s-1.338 2.567-2.171 3.556c-.834.99-2.326 2.732-4.167 3.603-1.842.872-2.808 1.036-4.628.849-1.82-.188-3.51-1.319-4.102-1.79-.592-.472-2.106-1.861-2.962-3.156C63.317 33.59 61.98 31 61.98 31s.745 2.596 1.212 3.698c.269.635 1.094 2.574 2.265 4.262 1.092 1.576 3.214 4.287 6.438 4.899 3.224.613 5.44-.942 5.987-1.319.549-.376 1.704-1.416 2.436-2.256.763-.877 1.486-1.995 1.886-2.666.292-.49.768-1.485.768-1.485z"></path> </g> </g> </svg> </a> <a href="http://w3.org/WAI/" aria-label="Web Accessibility Initiative"> <svg xmlns="http://www.w3.org/2000/svg" height="2em" viewBox="0 0 162.5 45.9"> <g fill="none" fill-rule="evenodd"> <path d="M0 0h162.5v45.9H0z" fill="#015a9c"></path> <path d="M1.2 24.5h160" stroke="#eed009" stroke-linecap="square" stroke-width="2"></path> <g fill="#fff" fill-rule="nonzero"> <path d="M15.741 15.5h-1.816L11.14 6.145c-.41-1.394-.65-2.334-.722-2.823-.104.749-.332 1.71-.684 2.881L7.04 15.5H5.223L1.444 1.223H3.32l2.217 8.72c.3 1.14.527 2.272.684 3.399.143-1.068.397-2.237.761-3.506l2.52-8.613h1.855l2.627 8.681c.339 1.127.6 2.272.781 3.438.105-.899.336-2.038.694-3.418l2.207-8.701h1.875zm10.127.195c-1.608 0-2.87-.486-3.784-1.46-.915-.973-1.372-2.312-1.372-4.018 0-1.719.426-3.088 1.279-4.107.853-1.019 2.005-1.528 3.457-1.528 1.348 0 2.422.435 3.223 1.304.8.869 1.2 2.046 1.2 3.53v1.064h-7.343c.033 1.218.342 2.142.928 2.774.586.631 1.416.947 2.49.947a8.46 8.46 0 001.631-.151c.514-.101 1.116-.298 1.807-.591v1.543a8.506 8.506 0 01-1.67.537c-.521.104-1.136.156-1.846.156zm-.44-9.677c-.84 0-1.503.27-1.992.81-.488.54-.778 1.292-.869 2.256h5.46c-.014-1.003-.245-1.764-.694-2.285-.45-.521-1.084-.781-1.904-.781zm12.237-1.416c1.413 0 2.503.486 3.271 1.46.769.973 1.153 2.332 1.153 4.077 0 1.77-.39 3.14-1.172 4.106-.781.967-1.865 1.45-3.252 1.45-.723 0-1.367-.13-1.934-.39a3.384 3.384 0 01-1.386-1.162h-.137a48.165 48.165 0 01-.362 1.357h-1.26V.305h1.759v3.691c0 .736-.033 1.471-.098 2.207h.098c.722-1.068 1.829-1.601 3.32-1.601zm-.293 1.455c-1.08 0-1.856.306-2.324.918-.47.612-.703 1.647-.703 3.105v.078c0 1.465.239 2.512.717 3.14.479.628 1.262.942 2.349.942.963 0 1.681-.353 2.153-1.06.472-.706.708-1.726.708-3.06 0-1.355-.237-2.37-.713-3.048-.475-.677-1.204-1.015-2.187-1.015zM59.286 15.5l-1.719-4.424h-5.664l-1.7 4.424h-1.816l5.577-14.336h1.62L61.152 15.5zM57.03 9.484L55.43 5.158l-.684-2.138c-.195.78-.4 1.494-.615 2.138l-1.621 4.326zm10.137 6.211c-1.543 0-2.744-.473-3.604-1.42-.86-.948-1.289-2.307-1.289-4.078 0-1.797.435-3.182 1.304-4.155.87-.973 2.108-1.46 3.716-1.46.52 0 1.037.054 1.548.161.51.108.932.246 1.264.415l-.537 1.465c-.905-.338-1.676-.508-2.314-.508-1.081 0-1.879.34-2.393 1.02-.514.681-.771 1.695-.771 3.043 0 1.295.257 2.287.771 2.973.514.687 1.276 1.03 2.285 1.03.944 0 1.872-.208 2.783-.624v1.562c-.742.384-1.663.576-2.763.576zm9.6 0c-1.544 0-2.745-.473-3.604-1.42-.86-.948-1.29-2.307-1.29-4.078 0-1.797.435-3.182 1.305-4.155.869-.973 2.107-1.46 3.715-1.46.521 0 1.037.054 1.548.161.511.108.933.246 1.265.415l-.537 1.465c-.905-.338-1.677-.508-2.315-.508-1.08 0-1.878.34-2.392 1.02-.515.681-.772 1.695-.772 3.043 0 1.295.257 2.287.772 2.973.514.687 1.276 1.03 2.285 1.03.944 0 1.872-.208 2.783-.624v1.562c-.742.384-1.663.576-2.764.576zm9.863 0c-1.608 0-2.87-.486-3.784-1.46-.915-.973-1.373-2.312-1.373-4.018 0-1.719.427-3.088 1.28-4.107.853-1.019 2.005-1.528 3.457-1.528 1.347 0 2.422.435 3.222 1.304.801.869 1.202 2.046 1.202 3.53v1.064H83.29c.032 1.218.342 2.142.928 2.774.586.631 1.416.947 2.49.947a8.46 8.46 0 001.63-.151c.515-.101 1.117-.298 1.807-.591v1.543a8.506 8.506 0 01-1.67.537c-.52.104-1.136.156-1.845.156zm-.44-9.677c-.84 0-1.504.27-1.992.81s-.778 1.292-.87 2.256h5.46c-.013-1.003-.244-1.764-.693-2.285-.45-.521-1.084-.781-1.905-.781zm14.14 6.523c0 1.003-.373 1.779-1.122 2.33-.749.55-1.8.824-3.154.824-1.413 0-2.536-.224-3.37-.674V13.42c1.179.573 2.315.86 3.409.86.885 0 1.53-.144 1.933-.43.404-.287.606-.671.606-1.153 0-.423-.194-.781-.581-1.074-.388-.293-1.076-.628-2.066-1.006-1.009-.39-1.719-.724-2.129-1-.41-.277-.711-.588-.903-.933-.192-.345-.288-.765-.288-1.26 0-.88.358-1.572 1.074-2.08.716-.508 1.7-.762 2.95-.762a8.17 8.17 0 013.417.723L99.511 6.7c-1.088-.456-2.068-.683-2.94-.683-.73 0-1.282.115-1.66.346-.378.231-.566.549-.566.952 0 .391.162.715.488.972.325.257 1.084.614 2.275 1.07.892.331 1.551.64 1.978.927.426.287.74.609.942.967.202.358.303.788.303 1.289zm9.58 0c0 1.003-.373 1.779-1.122 2.33-.749.55-1.8.824-3.154.824-1.413 0-2.536-.224-3.37-.674V13.42c1.179.573 2.315.86 3.409.86.885 0 1.53-.144 1.933-.43.404-.287.606-.671.606-1.153 0-.423-.194-.781-.581-1.074-.388-.293-1.076-.628-2.066-1.006-1.009-.39-1.719-.724-2.129-1-.41-.277-.71-.588-.903-.933-.192-.345-.288-.765-.288-1.26 0-.88.358-1.572 1.074-2.08.716-.508 1.7-.762 2.95-.762a8.17 8.17 0 013.417.723l-.595 1.396c-1.088-.456-2.067-.683-2.94-.683-.729 0-1.282.115-1.66.346-.378.231-.566.549-.566.952 0 .391.162.715.488.972.325.257 1.084.614 2.275 1.07.892.331 1.551.64 1.978.927.426.287.74.609.942.967.202.358.303.788.303 1.289zm4.356 2.959h-1.757V4.777h1.757zm-1.894-13.623c0-.39.1-.674.298-.85.198-.175.444-.263.737-.263.273 0 .513.088.718.263.205.176.307.46.307.85 0 .384-.102.667-.307.85a1.047 1.047 0 01-.718.273 1.05 1.05 0 01-.737-.273c-.199-.183-.298-.466-.298-.85zm10.371 2.725c1.413 0 2.503.486 3.271 1.46.769.973 1.153 2.332 1.153 4.077 0 1.77-.39 3.14-1.172 4.106-.781.967-1.865 1.45-3.252 1.45-.723 0-1.367-.13-1.934-.39a3.384 3.384 0 01-1.386-1.162h-.137a48.244 48.244 0 01-.361 1.357h-1.26V.305h1.758v3.691c0 .736-.033 1.471-.098 2.207h.098c.722-1.068 1.83-1.601 3.32-1.601zm-.293 1.455c-1.08 0-1.855.306-2.324.918-.469.612-.703 1.647-.703 3.105v.078c0 1.465.239 2.512.717 3.14.479.628 1.262.942 2.35.942.963 0 1.68-.353 2.152-1.06.472-.706.708-1.726.708-3.06 0-1.355-.237-2.37-.713-3.048-.475-.677-1.204-1.015-2.187-1.015zm9.277 9.443h-1.757V4.777h1.757zm-1.894-13.623c0-.39.1-.674.298-.85.198-.175.444-.263.737-.263.273 0 .513.088.718.263.205.176.307.46.307.85 0 .384-.102.667-.307.85a1.047 1.047 0 01-.718.273 1.05 1.05 0 01-.737-.273c-.199-.183-.298-.466-.298-.85zm7.05 13.623h-1.757V.305h1.758zm5.157 0h-1.758V4.777h1.758zm-1.895-13.623c0-.39.1-.674.298-.85.199-.175.444-.263.737-.263.274 0 .513.088.718.263.205.176.308.46.308.85 0 .384-.103.667-.308.85a1.047 1.047 0 01-.718.273 1.05 1.05 0 01-.737-.273c-.198-.183-.298-.466-.298-.85zm8.877 12.383c.228 0 .495-.023.801-.069.306-.045.537-.097.693-.156v1.348c-.162.071-.415.141-.756.21a5.29 5.29 0 01-1.04.102c-2.097 0-3.145-1.103-3.145-3.31v-6.24h-1.514v-.84l1.534-.703.703-2.286h1.045v2.461h3.095v1.368h-3.095v6.19c0 .62.148 1.095.444 1.427.296.332.708.498 1.235.498zm1.953-9.483h1.885l2.315 6.104c.488 1.328.787 2.301.898 2.92h.078c.059-.241.192-.692.4-1.353.209-.66.385-1.19.528-1.587l2.178-6.084h1.894l-4.619 12.207c-.45 1.185-.983 2.035-1.602 2.55-.618.514-1.383.77-2.294.77-.489 0-.974-.055-1.456-.165v-1.397c.326.078.717.117 1.172.117.56 0 1.035-.154 1.426-.463.39-.31.71-.787.957-1.431l.557-1.426zM7.157 45.5H2.001v-1.035l1.68-.381V32.658l-1.68-.4v-1.035h5.156v1.035l-1.68.4v11.426l1.68.38zm9.824 0v-6.855c0-.873-.193-1.522-.58-1.949-.388-.426-.995-.64-1.822-.64-1.1 0-1.9.305-2.398.914-.498.608-.747 1.6-.747 2.973V45.5H9.677V34.777h1.416l.263 1.465h.098a3.31 3.31 0 011.396-1.225 4.492 4.492 0 011.983-.435c1.315 0 2.292.319 2.93.957.638.638.957 1.63.957 2.979V45.5zm6.817 0H22.04V34.777h1.758zm-1.895-13.623c0-.39.1-.674.298-.85.199-.175.444-.263.737-.263.274 0 .513.088.718.263.205.176.308.46.308.85 0 .384-.103.667-.308.85a1.047 1.047 0 01-.718.273 1.05 1.05 0 01-.737-.273c-.199-.183-.298-.466-.298-.85zM30.78 44.26c.228 0 .495-.023.8-.069.307-.045.538-.097.694-.156v1.348c-.163.071-.415.141-.757.21a5.29 5.29 0 01-1.04.102c-2.096 0-3.144-1.103-3.144-3.31v-6.24h-1.514v-.84l1.533-.703.703-2.286H29.1v2.461h3.096v1.368H29.1v6.19c0 .62.149 1.095.445 1.427.296.332.708.498 1.235.498zm5.39 1.24h-1.757V34.777h1.758zm-1.894-13.623c0-.39.1-.674.298-.85.199-.175.444-.263.737-.263.274 0 .513.088.718.263.205.176.308.46.308.85 0 .384-.103.667-.308.85a1.047 1.047 0 01-.718.273 1.05 1.05 0 01-.737-.273c-.199-.183-.298-.466-.298-.85zM46.19 45.5l-.342-1.523h-.078c-.534.67-1.066 1.124-1.596 1.362-.53.237-1.2.356-2.007.356-1.055 0-1.882-.276-2.48-.83-.6-.553-.9-1.334-.9-2.344 0-2.174 1.716-3.313 5.147-3.417l1.817-.069V38.4c0-.813-.176-1.414-.528-1.801-.351-.388-.914-.581-1.689-.581-.566 0-1.102.084-1.606.253-.505.17-.979.359-1.421.567l-.537-1.318a7.958 7.958 0 011.767-.674 7.642 7.642 0 011.895-.244c1.295 0 2.259.286 2.89.859.632.573.948 1.484.948 2.734V45.5zm-3.623-1.22c.983 0 1.756-.266 2.32-.797.563-.53.844-1.284.844-2.26v-.967l-1.582.068c-1.23.046-2.127.241-2.69.586-.563.345-.845.889-.845 1.631 0 .56.171.99.513 1.29.342.299.822.448 1.44.448zm11.807-.02c.228 0 .495-.023.8-.069.307-.045.538-.097.694-.156v1.348c-.163.071-.415.141-.757.21a5.29 5.29 0 01-1.04.102c-2.096 0-3.144-1.103-3.144-3.31v-6.24h-1.514v-.84l1.533-.703.703-2.286h1.045v2.461h3.096v1.368h-3.096v6.19c0 .62.148 1.095.444 1.427.297.332.708.498 1.236.498zm5.39 1.24h-1.757V34.777h1.757zM57.87 31.877c0-.39.1-.674.298-.85.198-.175.444-.263.737-.263.274 0 .513.088.718.263.205.176.307.46.307.85 0 .384-.102.667-.307.85a1.047 1.047 0 01-.718.273 1.05 1.05 0 01-.737-.273c-.199-.183-.298-.466-.298-.85zM65.526 45.5l-4.062-10.723h1.884l2.276 6.319c.45 1.27.736 2.216.86 2.842h.077a11.495 11.495 0 01.176-.64c.04-.127.28-.861.723-2.202l2.285-6.319h1.875L67.548 45.5zm12.354.195c-1.608 0-2.87-.486-3.784-1.46-.915-.973-1.373-2.312-1.373-4.018 0-1.719.427-3.088 1.28-4.107.853-1.019 2.005-1.528 3.457-1.528 1.347 0 2.422.435 3.222 1.304.801.869 1.202 2.046 1.202 3.53v1.064H74.54c.032 1.218.342 2.142.928 2.774.586.631 1.416.947 2.49.947a8.46 8.46 0 001.63-.151c.515-.101 1.117-.298 1.807-.591v1.543a8.506 8.506 0 01-1.67.537c-.52.104-1.136.156-1.845.156zm-.44-9.677c-.84 0-1.504.27-1.992.81s-.778 1.292-.87 2.256h5.46c-.013-1.003-.244-1.764-.693-2.285-.45-.521-1.084-.781-1.905-.781zM137.741 45.5h-1.816l-2.784-9.355c-.41-1.394-.65-2.334-.722-2.823-.104.749-.332 1.71-.684 2.881L129.04 45.5h-1.817l-3.779-14.277h1.875l2.217 8.72c.3 1.14.527 2.272.684 3.399.143-1.068.397-2.237.761-3.506l2.52-8.613h1.855l2.627 8.681c.339 1.127.6 2.272.781 3.438.105-.899.336-2.038.694-3.418l2.207-8.701h1.875zm14.57 0l-1.718-4.424h-5.664l-1.7 4.424h-1.816l5.576-14.336h1.621l5.567 14.336zm-2.256-6.016l-1.601-4.326-.684-2.138c-.195.78-.4 1.494-.615 2.138l-1.621 4.326zm10.098 6.016h-5.156v-1.035l1.68-.381V32.658l-1.68-.4v-1.035h5.156v1.035l-1.68.4v11.426l1.68.38z"></path> </g> </g> </svg> </a> </div> </header> </div> <div class="default-grid nav-container nav-page-specific"> <div class="nav"> <nav class="nav standalone-resource-pager" aria-label="Understanding Docs"> <ul> <li class="nav__item"> <a href=".">All Understanding Docs</a> </li> <li class="nav__item"> <a href="input-assistance"> <svg focusable="false" aria-hidden="true" class="icon-arrow-left-thin pager-icon" viewBox="0 0 16 16"> <path fill-rule="evenodd" d="M12 8a.5.5 0 0 1-.5.5H5.707l2.147 2.146a.5.5 0 0 1-.708.708l-3-3a.5.5 0 0 1 0-.708l3-3a.5.5 0 1 1 .708.708L5.707 7.5H11.5a.5.5 0 0 1 .5.5z"></path> </svg> Previous Guideline: Input Assistance </a> </li> </ul> </nav> </div> </div> <div class="default-grid with-gap leftcol"> <aside class="box nav-hack sidebar standalone-resource__sidebar"> <header class="box-h">Page Contents</header> <div class="box-i"> <nav aria-label="page contents" class="navtoc"> <ul><li><a href="#guideline">Guideline</a></li> <li><a href="#intent">Intent</a></li> <li><a href="#success-criteria">Success Criteria</a></li> </ul> </nav> </div> </aside> <main id="main" class="standalone-resource__main"> <h1> <span class="standalone-resource__type-of-guidance"> Understanding <a href="https://w3.org/TR/WCAG21#compatible">Guideline 4.1</a>: </span>Compatible </h1> <section id="guideline" class="box"> <h2 class="box-h box-h-icon">Guideline</h2> <div class="box-i"><p>Maximize compatibility with current and future user agents, including assistive technologies.</p></div> </section> <section id="intent"> <h2>Intent</h2> <p>The purpose of this guideline is to support compatibility with current and future user agents, <em>especially</em> assistive technologies (AT). This is done both by 1) ensuring that authors do not do things that would break AT (e.g., poorly formed markup) or circumvent AT (e.g., by using unconventional markup or code) and 2) exposing information in the content in standard ways that assistive technologies can recognize and interact with. Since technologies change quickly, and AT developers have much trouble keeping up with rapidly changing technologies, it is important that content follow conventions and be compatible with APIs so that AT can more easily work with new technologies as they evolve. </p> </section> <section id="success-criteria"> <h2>Success Criteria for this Guideline</h2> <ul> <li><a href="parsing">4.1.1 Parsing</a></li> <li><a href="name-role-value">4.1.2 Name, Role, Value</a></li> <li><a href="status-messages">4.1.3 Status Messages</a></li> </ul> </section> <a class="button button-backtotop" href="#top"> <span> <svg focusable="false" aria-hidden="true" class="icon-arrow-up " viewBox="0 0 26 28"> <path d="M25.172 15.172c0 0.531-0.219 1.031-0.578 1.406l-1.172 1.172c-0.375 0.375-0.891 0.594-1.422 0.594s-1.047-0.219-1.406-0.594l-4.594-4.578v11c0 1.125-0.938 1.828-2 1.828h-2c-1.062 0-2-0.703-2-1.828v-11l-4.594 4.578c-0.359 0.375-0.875 0.594-1.406 0.594s-1.047-0.219-1.406-0.594l-1.172-1.172c-0.375-0.375-0.594-0.875-0.594-1.406s0.219-1.047 0.594-1.422l10.172-10.172c0.359-0.375 0.875-0.578 1.406-0.578s1.047 0.203 1.422 0.578l10.172 10.172c0.359 0.375 0.578 0.891 0.578 1.422z"></path> </svg> Back to Top </span> </a> </main> <aside class="box box-icon box-space-above" id="helpimprove" style="grid-column: 2 / 8; grid-row: 3"> <header class="box-h box-h-icon box-h-space-above box-h-icon"> <svg focusable="false" aria-hidden="true" class="icon-comments" viewBox="0 0 28 28"> <path d="M22 12c0 4.422-4.922 8-11 8-0.953 0-1.875-0.094-2.75-0.25-1.297 0.922-2.766 1.594-4.344 2-0.422 0.109-0.875 0.187-1.344 0.25h-0.047c-0.234 0-0.453-0.187-0.5-0.453v0c-0.063-0.297 0.141-0.484 0.313-0.688 0.609-0.688 1.297-1.297 1.828-2.594-2.531-1.469-4.156-3.734-4.156-6.266 0-4.422 4.922-8 11-8s11 3.578 11 8zM28 16c0 2.547-1.625 4.797-4.156 6.266 0.531 1.297 1.219 1.906 1.828 2.594 0.172 0.203 0.375 0.391 0.313 0.688v0c-0.063 0.281-0.297 0.484-0.547 0.453-0.469-0.063-0.922-0.141-1.344-0.25-1.578-0.406-3.047-1.078-4.344-2-0.875 0.156-1.797 0.25-2.75 0.25-2.828 0-5.422-0.781-7.375-2.063 0.453 0.031 0.922 0.063 1.375 0.063 3.359 0 6.531-0.969 8.953-2.719 2.609-1.906 4.047-4.484 4.047-7.281 0-0.812-0.125-1.609-0.359-2.375 2.641 1.453 4.359 3.766 4.359 6.375z"></path> </svg> <h2>Help improve this page</h2> </header> <div class="box-i"> <p>Please share your ideas, suggestions, or comments via e-mail to the publicly-archived list <a href="mailto:public-agwg-comments@w3.org?subject=%5BUnderstanding%20and%20Techniques%20Feedback%5D">public-agwg-comments@w3.org</a> or via GitHub</p> <div class="button-group"> <a href="mailto:public-agwg-comments@w3.org?subject=%5BUnderstanding%20and%20Techniques%20Feedback%5D" class="button"><span>E-mail</span></a> <a href="https://github.com/w3c/wcag/issues/" class="button"><span>Fork & Edit on GitHub</span></a> <a href="https://github.com/w3c/wcag/issues/new" class="button"><span>New GitHub Issue</span></a> </div> </div> </aside> </div> <footer id="wai-site-footer" class="page-footer default-grid" aria-label="Page"> <div class="inner" style="grid-column: 2 / 8"> <p><strong>Date:</strong> Updated 02 April 2024.</p> <p><strong>Developed by</strong> <a href="https://www.w3.org/groups/wg/ag/participants">Accessibility Guidelines Working Group (AG WG) Participants</a> (Co-Chairs: Alastair Campbell, Charles Adams, Rachael Bradley Montgomery. W3C Staff Contact: Michael Cooper). </p> <p>The content was developed as part of the <a href="https://www.w3.org/WAI/about/projects/#us">WAI-Core projects</a> funded by U.S. Federal funds. The user interface was designed by the Education and Outreach Working Group (<a href="https://www.w3.org/groups/wg/eowg/participants">EOWG</a>) with contributions from Shadi Abou-Zahra, Steve Lee, and Shawn Lawton Henry as part of the <a href="https://www.w3.org/WAI/about/projects/wai-guide/">WAI-Guide</a> project, co-funded by the European Commission. </p> </div> </footer> <footer class="site-footer grid-4q" aria-label="Site"> <div class="q1-start q3-end about"> <div> <p><a class="largelink" href="https://www.w3.org/WAI/" dir="auto" translate="no" lang="en">W3C Web Accessibility Initiative (WAI)</a></p> <p>Strategies, standards, and supporting resources to make the Web accessible to people with disabilities.</p> </div> <div class="social" dir="auto" translate="no" lang="en"> <ul> <li><a href="https://twitter.com/w3c_wai"><svg focusable="false" aria-hidden="true" class="icon-twitter " viewBox="0 0 32 32"><path d="M31.939 6.092c-1.18 0.519-2.44 0.872-3.767 1.033 1.352-0.815 2.392-2.099 2.884-3.631-1.268 0.74-2.673 1.279-4.169 1.579-1.195-1.279-2.897-2.079-4.788-2.079-3.623 0-6.56 2.937-6.56 6.556 0 0.52 0.060 1.020 0.169 1.499-5.453-0.257-10.287-2.876-13.521-6.835-0.569 0.963-0.888 2.081-0.888 3.3 0 2.28 1.16 4.284 2.917 5.461-1.076-0.035-2.088-0.331-2.971-0.821v0.081c0 3.18 2.257 5.832 5.261 6.436-0.551 0.148-1.132 0.228-1.728 0.228-0.419 0-0.82-0.040-1.221-0.115 0.841 2.604 3.26 4.503 6.139 4.556-2.24 1.759-5.079 2.807-8.136 2.807-0.52 0-1.039-0.031-1.56-0.089 2.919 1.859 6.357 2.945 10.076 2.945 12.072 0 18.665-9.995 18.665-18.648 0-0.279 0-0.56-0.020-0.84 1.281-0.919 2.4-2.080 3.28-3.397l-0.063-0.027z"></path></svg> Twitter</a></li> <li><a href="https://www.w3.org/WAI/feed.xml"><svg focusable="false" aria-hidden="true" class="icon-rss " viewBox="0 0 32 32"><path d="M25.599 32c0-14.044-11.555-25.6-25.599-25.6v-6.4c17.553 0 32 14.447 32 32h-6.401zM4.388 23.22c2.419 0 4.391 1.972 4.391 4.393 0 2.417-1.98 4.387-4.401 4.387-2.417 0-4.377-1.965-4.377-4.387s1.967-4.392 4.388-4.393zM21.212 32h-6.22c0-8.225-6.767-14.993-14.992-14.993v-6.22c11.636 0 21.212 9.579 21.212 21.213z"></path></svg> Feed</a></li> <li><a href="https://www.youtube.com/channel/UCU6ljj3m1fglIPjSjs2DpRA/playlistsv"><svg focusable="false" aria-hidden="true" class="icon-youtube " viewBox="0 0 32 32"><path d="M31.327 8.273c-0.386-1.353-1.431-2.398-2.756-2.777l-0.028-0.007c-2.493-0.668-12.528-0.668-12.528-0.668s-10.009-0.013-12.528 0.668c-1.353 0.386-2.398 1.431-2.777 2.756l-0.007 0.028c-0.443 2.281-0.696 4.903-0.696 7.585 0 0.054 0 0.109 0 0.163l-0-0.008c-0 0.037-0 0.082-0 0.126 0 2.682 0.253 5.304 0.737 7.845l-0.041-0.26c0.386 1.353 1.431 2.398 2.756 2.777l0.028 0.007c2.491 0.669 12.528 0.669 12.528 0.669s10.008 0 12.528-0.669c1.353-0.386 2.398-1.431 2.777-2.756l0.007-0.028c0.425-2.233 0.668-4.803 0.668-7.429 0-0.099-0-0.198-0.001-0.297l0 0.015c0.001-0.092 0.001-0.201 0.001-0.31 0-2.626-0.243-5.196-0.708-7.687l0.040 0.258zM12.812 20.801v-9.591l8.352 4.803z"></path></svg> YouTube</a></li> <li><a href="https://www.w3.org/WAI/news/subscribe/" class="button">Get News in Email</a></li> </ul> </div> <div dir="auto" translate="no" lang="en"> <p>Copyright 漏 2025 World Wide Web Consortium (<a href="https://www.w3.org/">W3C</a><sup>庐</sup>). See <a href="/WAI/about/using-wai-material/">Permission to Use WAI Material</a>.</p> </div> </div> <div dir="auto" translate="no" class="q4-start q4-end" lang="en"> <ul style="margin-bottom:0"> <li><a href="/WAI/about/contacting/">Contact WAI</a></li> <li><a href="/WAI/sitemap/">Site Map</a></li> <li><a href="/WAI/news/">News</a></li> <li><a href="/WAI/about/accessibility-statement/">Accessibility Statement</a></li> <li><a href="/WAI/translations/"> Translations</a></li> <li><a href="/WAI/roles/">Resources for Roles</a></li> </ul> </div> </footer> <link rel="stylesheet" href="../a11y-light.css"> <script src="../highlight.min.js"></script> <script> hljs.configure({ cssSelector: 'pre' }); hljs.highlightAll(); var translationStrings = {}; /* fix WAI JS */ </script> <script src="https://www.w3.org/WAI/assets/scripts/main.js"></script> <script> var _paq = _paq || []; /* tracker methods like "setCustomDimension" should be called before "trackPageView" */ _paq.push(["setDoNotTrack", true]); _paq.push(['trackPageView']); _paq.push(['enableLinkTracking']); (function () { var u = "//www.w3.org/analytics/piwik/"; _paq.push(['setTrackerUrl', u + 'piwik.php']); _paq.push(['setSiteId', '328']); var d = document, g = d.createElement('script'), s = d.getElementsByTagName('script')[0]; g.type = 'text/javascript'; g.async = true; g.defer = true; g.src = u + 'piwik.js'; s.parentNode.insertBefore(g, s); })(); </script> <noscript> <p><img src="//www.w3.org/analytics/piwik/piwik.php?idsite=328&rec=1" style="border:0;" alt="" /></p> </noscript> </body></html>