This feature allows pages to disable the running of unload event handlers. The goal is to : - allow sites that have removed all unload handlers to ensure they do not accidentally add new ones - allow sites to remove unload handlers when updating the code would is infeasible Unload event handlers are problematic for various reasons and prevent use of BFCache on Desktop (see


Help sites migrate off unload event handlers and thereby improve BFCache hit-rate: - by ensuring that once removed, handlers do not creep back in - by providing a means to disable handlers in 3rd party iframes and script that is hard to change


Specification link

Proposal in a personal repository, no adoption from community

Status in Chromium


No active development (tracking bug)

Consensus & Standardization

After a feature ships in Chrome, the values listed here are not guaranteed to be up to date.

  • Negative
  • No signal
  • Positive


Intent to Prototype url

Intent to Prototype thread

Last updated on 2022-05-13