Accessibility
You should never treat the unload event as a guaranteed callback, using it as an end-of-session signal to send analytical data and save state.
In fact, in many download situations the unload event will not fire.
Always rely on the visibilitychange event if you want to determine when a session ends, and as the last reliable time to save both app and user data, consider the state hidden.
Browsers can only be prevented from caching pages Back-Forward by the presence of a registered unload event handler (via onunload or addEventListener()).
It is therefore advisable to use the pagehide event on all modern browsers (including IE11) in order to detect page unloads.
const terminationEvent = 'onpagehide' in self ? 'pagehide' : 'unload'; addEventListener(terminationEvent, (event) => { // Note: if the browser is able to cache the page, `event.persisted` // is `true`, and the state is frozen rather than terminated. }, {capture: true});
Learn more about Accessibility
On page SEO performance and page checkup.
Over 300 parameters for the deeper page analysis.
Share this Guide
Did you like it? Share it!
Web tools for modern developers. Try these one!
Over 50 generators, builders and validators to improve your SEO and web performances
Tester and validators
Validate your Css file sheet with W3C validation Service. Check if the markup of your Cascading style Sheet document is W3C compliant.
Server and proxy
Retrieve remote Server Status Code and Headers. Get HTTP Status code, Headers info, Cache-control and data from a given URL.
Capture web page requests and timeline waterfall. Quickly capture and analyze web page network requests during page load.
Images
Quicly capture any web page screenshot and thumbnails. Get image rendering on desktop and mobile and thumbnails filmstrip with loading timing.
Social Tester and validators
Get Facebook data and engagement count by URL. Retrieve Open Graph data, "share" count, comment count and engagement from url.
Test your Progressive Web App. Check the performance of your PWA, try to deliver high quality, engaging, fast and capable apps on every devices.
Converters
Convert Bits, Bytes, Kilobytes, Megabytes, Gigabytes, Terabytes and so on. Set number and choose unit to convert. Try it for free.
Check SEO performance and page checkup. Over 250 parameters for the deeper page analysis. Find out more about the performance of your website.