[BaconMan1168]

Description

This PR removes the claim that Firefox won't put pages with beforeunload listeners in the bfcache, along with the same claim on the sendBeacon() and pagehide pages.

Motivation

• The beforeunload usage notes said Firefox excludes pages with beforeunload listeners from the bfcache. Firefox has allowed these pages in the bfcache since version 116, so I removed the bullet. That left a one-item list, so I turned it into a paragraph. I also removed the sentence saying that listening sparingly minimizes the effect on performance, since the removed bullet was the only reason given for it.
• The "Legacy events" section of the sendBeacon() page had a separate line saying Firefox excludes pages with beforeunload handlers, which I removed. The comparison with pagehide now only mentions unload.
• The pagehide page said pagehide is compatible with the bfcache "unlike the unload and beforeunload events". It now only mentions unload.

Additional details

• Firefox bugs: 1837045 (enabled in release, Firefox 116) and 1741671 (enabled in Nightly).
• The docshell.shistory.bfcache.ship_allow_beforeunload_listeners pref now defaults to true on all platforms in Firefox's current source.
• markdownlint-cli2 and prettier --check report 0 issues on the changed files, and the front-matter linter passes.

Related issues and pull requests

Fixes #46214

[github-actions]

Preview URLs (3 pages)

• /en-US/docs/Web/API/Navigator/sendBeacon
• /en-US/docs/Web/API/Window/beforeunload_event
• /en-US/docs/Web/API/Window/pagehide_event

External URLs (2)

URL: /en-US/docs/Web/API/Window/beforeunload_event
Title: Window: beforeunload event

• https://www.igvita.com/2015/11/20/dont-lose-user-and-app-state-use-page-visibility/ (1 time) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/Web/API/Window/pagehide_event
Title: Window: pagehide event

• https://web.dev/articles/bfcache (2 times) (Note! This may be a new URL 👀)

(comment last updated: 2026-10-25 22:38:49)

[github-actions]

[mdn-linter] _{reported by reviewdog 🐶}

Suggested change

	The `beforeunload` event is not reliably fired, especially on mobile platforms. For example, the event is not fired in the following scenario:
	The `beforeunload` event is not reliably fired, especially on mobile platforms. For example, the event is not fired in the following scenario:

[hamishwillee]

Thanks very much!