PSA: Enabling BFCache for pages using Shared Workers

[Anna Sato]

Hi blink-dev,

In Chrome M146, we plan to enable the back/forward cache (BFCache) for pages that use Shared Workers.

Previously, the usage of Shared Workers blocked pages from entering BFCache. We have been experimenting with removing this restriction, and we are now ready to enable this behavior by default.

With this change, pages holding a Shared Worker connection will be eligible for BFCache. However, please be aware of the following eviction behaviors:

• Message from Worker: If a page in BFCache receives a message from a Shared Worker, the page will be evicted.
• All connections cached: If all pages connected to a Shared Worker enter BFCache, those pages will be evicted because the Shared Worker is no longer actively needed.

You can view the relevant HTML spec changes in this GitHub PR.

Separately, we are working on a change to freeze the Shared Worker and keep storing the pages instead of evicting them when all connected pages are in BFCache. We plan to start a Finch experiment for this behavior soon.

Thanks,

Anna