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updown.io – Website monitoring, simple and inexpensive
<!DOCTYPE html> <html lang="en"> <head> <title>updown.io – Website monitoring, simple and inexpensive</title> <meta content="ϟ Website monitoring — beautiful, simple and inexpensive." name="description" /> <link rel="icon" type="image/png" href="https://updown.io/favicon.png" /> <meta charset="utf-8" /> <meta content="width=device-width, initial-scale=1" name="viewport" /> <meta content="#f9f9f9" name="theme-color" /> <link href="/apple-touch-icon.png" rel="apple-touch-icon" /><meta name="csrf-param" content="authenticity_token" /> <meta name="csrf-token" content="OD25Fgfay8pPjGlF8vyz467KXvM2fSwR-2p16NPRKk0mFWbmxTtqnZv_V8UCxlnAy4LVzdb92OfAwsrusO7e5A" /><link rel="stylesheet" href="https://updown.io/assets/application-23c17ed0a7047a18cecd9bbf10bf4000a61a4a8346b8aaff19f10a46130413f8.css" media="all" /> </head> <body> <header> <div class="center"> <div id="logo"> <a href="/">⟠ updown.io</a> </div> <div id="session"> <div class="actions mono"> <a href="/#pricing">Pricing</a> <a class="btn-gray" href="/users/sign_in"><svg viewbox="0 0 20 20" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="icon icon-sign-in"><path d="M13 1h4a2 2 0 0 1 2 2v14a2 2 0 0 1-2 2h-4"></path><polyline points="8 15 13 10 8 5"></polyline><line x1="13" y1="10" x2="1" y2="10"></line></svg> Sign in</a> </div> </div> </div> </header> <section id="articles"> <div class="center"> <h2> <a class="black" href="/faq">FAQ</a> <svg viewbox="0 0 16 24" fill="none" stroke="hsl(35, 10%, 66%)" stroke-width="1.7" class="icon icon-chevron-right"><polyline points="6 3 11 13 6 23"></polyline></svg> What is APDEX? </h2> <p><strong>Apdex</strong> is a client perception based performance metric. It buckets requests in 3 categories depending on their <strong>response time</strong>: <em>Satisfied</em>, <em>Tolerating</em> and <em>Frustrated</em>.<br> It then computes a single number between 0 and 1 (higher the better) using the formula shown below.<br> Computing the Apdex requires a single parameter <strong>T</strong> "threshold" used to draw the line (in term of response time) between the 3 buckets: all requests faster than <strong>T</strong> are <em>Satisfied</em>, all requests between <strong>T</strong> and <strong>4×T</strong> are <em>Tolerating</em> and all other requests (above <strong>4×T</strong> or failed) are considered <em>Frustrated</em>.</p> <p><img src="/files/652e9c7b893e4a284b1e478e.png" alt="diagram explaining the previous definition with an example"></p> <p>Apdex is usually applied server-side, measuring only app response time. However, it is entirely possible to compute it client-side, as updown.io does. In this case, it also includes network latency, which is beneficial because your users experience it too. As a consequence it requires higher thresholds to account for the added delay.</p> <p>The Apdex threshold can be configured individually for each check:</p> <p><img src="/files/652e9516893e4a284b1e45b2.png" alt="screenshot of updown UI showing the Apdex threshold selector"></p> <p>And any change to this value will immediately impact the dashboard and status page charts.</p> <p>We recommend setting the Apdex <strong>T</strong> just above your usual response times, for example in this case 0.5 would be a good value:</p> <p><img src="/files/652e9538893e4a284b1e45c3.png" alt="screenshot of and updown status page response time chart"></p> <br /><div id="like" class="actions" rel="tooltip" title="Connected users only"><a disabled="disabled" class="btn-gray" data-remote="true" rel="nofollow" data-method="post" href="/articles/652e9551893e4a284b1e45cf/like"><svg height="24" viewbox="-1 -1 26 26" fill="none" stroke="currentColor" stroke-width="2.2" stroke-linejoin="round" class="icon icon-heart"><path d="M20.84 5.11a5.5 5.5 0 0 0-7.78 0L12 6.17l-1.06-1.06a5.5 5.5 0 0 0-7.78 7.78l1.06 1.06L12 21.73l7.78-7.78 1.06-1.06a5.5 5.5 0 0 0 0-7.78z"></path></svg>16 Like</a></div><div class="author"><svg height="24" viewbox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="icon icon-user"><path d="M20 21v-2a4 4 0 0 0-4-4H8a4 4 0 0 0-4 4v2"></path><circle cx="12" cy="7" r="4"></circle></svg> <strong>Adrien Rey-Jarthon</strong></div><small style="border-image: url('/articles/652e9551893e4a284b1e45cf/read')">Created on October 17, 2023 · Last update on February 19, 2025 </small> </div> </section> <footer> <div class="center"> <div class="support"> <a class="btn-dark-gray" href="/doc"><svg height="24" viewbox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="icon icon-book"><path d="M4 19.5A2.5 2.5 0 0 1 6.5 17H20"></path><path d="M6.5 2H20v20H6.5A2.5 2.5 0 0 1 4 19.5v-15A2.5 2.5 0 0 1 6.5 2z"></path><polygon points="9.5,8.5 14.5,8.5 12,5" fill="currentColor" stroke="none" opacity="0.7"></polygon><polygon points="9.5,10.5 14.5,10.5 12,14" fill="currentColor" stroke="none" opacity="0.7"></polygon></svg> Documention & FAQ</a> <a class="btn-dark-gray" target="_blank" href="mailto:support@updown.io?subject=%F0%9F%99%8B%20Please%20help"><svg height="24" viewbox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="icon icon-mail"><path d="M4 4h16c1.1 0 2 .9 2 2v12c0 1.1-.9 2-2 2H4c-1.1 0-2-.9-2-2V6c0-1.1.9-2 2-2z"></path><polyline points="22,6 12,13 2,6"></polyline></svg> Support</a><br /><a target="_blank" href="https://status.updown.io">System Status</a><br /><a target="_blank" href="https://twitter.com/updownio"><svg height="16" viewbox="0 0 1200 1227" fill="currentColor" class="icon icon-twitter"><path d="M714.163 519.284L1160.89 0H1055.03L667.137 450.887L357.328 0H0L468.492 681.821L0 1226.37H105.866L515.491 750.218L842.672 1226.37H1200L714.137 519.284H714.163ZM569.165 687.828L521.697 619.934L144.011 79.6944H306.615L611.412 515.685L658.88 583.579L1055.08 1150.3H892.476L569.165 687.854V687.828Z"></path></svg> Twitter</a> </div> <ul class="links"> <li> <a href="/api">API</a> </li> <li> <a href="/about">About</a> </li> <li> <a href="/blog">Blog</a> </li> <li> <a href="https://updown.canny.io">Feature requests</a> </li> </ul> <ul class="links"> <li> <a href="/tos">Terms of Service</a> </li> <li> <a href="/privacy_policy">Privacy Policy</a> </li> </ul> <div class="madein"> Made with <svg height="24" viewbox="-1 -1 26 26" fill="none" stroke="currentColor" stroke-width="2.2" stroke-linejoin="round" class="icon icon-heart"><path d="M20.84 5.11a5.5 5.5 0 0 0-7.78 0L12 6.17l-1.06-1.06a5.5 5.5 0 0 0-7.78 7.78l1.06 1.06L12 21.73l7.78-7.78 1.06-1.06a5.5 5.5 0 0 0 0-7.78z"></path></svg> in <a href="https://www.google.fr/maps/preview#!q=Paris">Paris, France</a> since 2012 </div> </div> </footer> <script src="https://updown.io/assets/application-04a9139f5883acb33207c805cf5b53affa48bc7db7218a7927782842080f6ad2.js"></script> </body> </html>