[wp-trac] [WordPress Trac] #63636: Enable instant page navigations from browser history via bfcache when sending "nocache" headers

[WordPress Trac]

#63636: Enable instant page navigations from browser history via bfcache when
sending "nocache" headers
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 Reporter:  westonruter                          |       Owner:
                                                 |  westonruter
     Type:  enhancement                          |      Status:  accepted
 Priority:  normal                               |   Milestone:  6.9
Component:  Administration                       |     Version:  6.3
 Severity:  normal                               |  Resolution:
 Keywords:  has-patch dev-feedback needs-unit-   |     Focuses:
  tests                                          |  performance, privacy
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Comment (by westonruter):

 Ideally the `pageshow` event wouldn't need to be relied on to use JS to
 invalidate pages from bfcache. While this works, it is somewhat of a hack,
 and there remains a possible split-millisecond in which a previously-
 authenticated page can appear prior to the `pageshow` event handler
 detecting the authentication state change and triggering a reload.

 There's also an [https://github.com/westonruter/nocache-bfcache/issues/53
 issue] I discovered when using a service worker to serve pages with a
 NetworkFirst strategy, where a page gets served from cache if the network
 doesn't respond before a timeout occurs. This can result in pages stored
 in Cache by the service worker which have stale bfcache session token, and
 then every navigation which returns such a page in cache will immediately
 reload once served from cache. Not ideal.

 The correct solution to protecting privacy is invaliding pages from
 bfcache using the `Clear-Site-Data: "cache"` response header, as
 [comment:4 mentioned above]. The benefit here is that there is no
 JavaScript involved at all. See also the [https://github.com/westonruter
 /nocache-bfcache/issues/22 feature plugin issue] I created for this.

 This header is [https://caniuse.com/mdn-http_headers_clear-site-data_cache
 well supported] by browsers. ''However'', there is currently a bug in
 Chromium ([https://issues.chromium.org/issues/40233601 40233601]) which
 causes page responses sent with this header to be very slow. I think this
 should be a blocker preventing this from moving forward until it is fixed.

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Ticket URL: <https://core.trac.wordpress.org/ticket/63636#comment:12>
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