Intent to ship Fetch Keepalive

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Sunil Mayya

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Oct 21, 2024, 5:52:05 AMOct 21

to dev-pl...@mozilla.org, Valentin Gosu, Gregory Hess, Eden Chuang

Dear All,

I would like to announce my intent to ship the fetch keepalive feature in Firefox 133.

The feature was enabled by default in Bug 1923044.

Feature Overview:
The keepalive option for the Fetch Request API allows developers to send requests even after the page has started unloading. This is particularly useful for sending analytics data, saving form data, or completing other tasks during page unload, without blocking the navigation.

Specification:
The feature is part of the Fetch Standard.

Platform Coverage:
The feature is already supported by all other major browsers.

Testing:
There is sufficient test coverage for this feature through Web Platform Tests. We have also added mozilla-specific web-platform tests.

Compatibility:

As indicated by the web-platform test results, the feature is largely compatible with other browsers. However, each browser implements restriction on number of keepalive requests in a non-compat way. We have restricted fetch keepalive requests based on their origin (250 per origin) along with a limit on total number of pending keepalive fetch requests (500 per browser instance).

Please let me know if you have any questions.

Regards