Microsoft has announced through its admin message centre that Edge will stop running unload event handlers by default. A phased rollout began in September 2026 and is expected to finish in October. Afterwards, pages that do not explicitly opt in through a Permissions-Policy header will no longer fire these handlers.

Microsoft says the event is unreliable, because browsers and operating systems can suspend or close a page without firing it, and that it can also stop a page from using the back/forward cache, which makes returning to a previous page instant.

Anyone running public sites or internal apps that save user data, release resources, send analytics or tell the server a session has ended using this event, with no fallback, may see different behaviour. WebView2 apps and managed Edge environments are affected too. A temporary workaround exists, an enterprise policy named ForcePermissionPolicyUnloadDefaultEnabled or enabling the event from the site, but Microsoft describes both as migration aids rather than permanent fixes.

The recommended path is to move saving logic to the visibilitychange event and use pagehide where back/forward-cache-friendly navigation handling is needed, after auditing which apps, including third-party libraries, register unload handlers.

What does this mean for your business?
If you run an employee portal, booking system or dashboard in the browser, ask your technical team whether any part depends on unload to save a draft or close a session. You may only notice when someone loses data after closing a tab. Checking early is far cheaper than recovering lost data, and moving to visibilitychange is a small change if planned before failures appear. For third-party systems, ask the vendor for written confirmation that they do not rely on this event.

Source: Microsoft message centre MC1449170 — https://mc.merill.net/message/MC1449170 , and Microsoft policy documentation — https://learn.microsoft.com/en-us/deployedge/microsoft-edge-policies/forcepermissionpolicyunloaddefaultenabled