bfcache

The back/forward cache, or bfcache, is a performance-enhancing feature available in modern browsers that enables instant back and forward navigation between previously-visited pages. It does this by storing a complete snapshot of a page as the user navigates away from it; the browser can then quickly restore the snapshot if the user decides to return to it, rather than needing to repeat the network requests required to load the page.

The snapshot contains the entire page in memory, including the JavaScript heap; in-progress code is paused when the user navigates away and resumed when they return to the page. A regular HTTP cache entry on the other hand contains only responses to previous requests. The bfcache therefore provides faster results than the HTTP cache.