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Explainer https://github.com/WICG/nav-speculation/blob/main/triggers.md#no-vary-search-hint Specification https://wicg.github.io/nav-speculation/prerendering.html Summary Adds a hint to speculation rules that informs the navigation prerender cache that the URL to be prerendered expects to receive the same No-Vary-Search header in the response. The hint is useful because prerenders that depend on No-Vary-Search to match to navigations do not benefit the user if the navigation happens before prerender headers return from the server. Using the hint, the web browser will expect, but verify, that the No-Vary-Search hint matches with the No-Vary-Search header. If the No-Vary-Search hint does not match the No-Vary-Search header received then the web browser will send a new request. We would like to ship "No-Vary-Search Hint for Prerender Speculation Rules" together with "No-Vary-Search support for prerender <https://chromestatus.com/feature/5099218903760896>". Blink component Internals>Preload>Prerender <https://bugs.chromium.org/p/chromium/issues/list?q=component:Internals%3EPreload%3EPrerender> TAG review Not applicable. The TAG has already given a negative opinion on the overall complexity of speculation rules ( https://github.com/w3ctag/design-reviews/issues/721 ), so we anticipate it would not be a good use of their time to review additions to the syntax. The addition itself is small and any architectural questions about it would be covered under the general closed speculation rules review. TAG review status Not applicable Risks Interoperability and Compatibility None Gecko: No signal ( https://github.com/mozilla/standards-positions/issues/620#issuecomment-1608195274 ) WebKit: No signal ( https://github.com/WebKit/standards-positions/issues/54#issuecomment-1608197504 ) Web developers: Below is the text from the I2S of the No-Vary-Search on navigational prefetch, and we believe the same applies to Prerendering. Google Search has been experimenting with No-Vary-Search header / Speculation Rules "expects_no_vary_search". This functionality helps Google Search to match prefetched content to the next user navigation. Developers can use parameters in the prefetched URL that are not needed when navigating to the actual link (e.g. the source of the link click). The server can customize behavior using these parameters without causing a cache miss in the browser. "expects_no_vary_search" addition to Speculation Rules allows the browser to completely handle the case where the user navigates to a URL that is currently prefetched by waiting for the ongoing prefetch instead of directly requesting the page from the server. Google Search conducted experiments prefetching Search results pages from the search box and other links that lead to another Search results page. There was significant latency improvement for navigating to Search result pages prefetched using No-Vary-Search header and "expects_no_vary_search". Other signals: No-Vary-Search header has been discussed, together with No-Vary-Search Hint for Prefetch Speculation Rules at Web Perf WG meeting at TPAC 2023. https://docs.google.com/presentation/u/1/d/1GK92nCORW5vKd7LgGtTsgy35eqTV7P71l05pHsni8ok/edit#slide=id.g240fd6541f7_0_31 Ergonomics (Text taken from Prefetch NVS I2S) No-Vary-Search will be used in tandem with Speculation Rules ( https://wicg.github.io/nav-speculation/speculation-rules.html). The default usage of No-Vary-Search will not make it hard for Chrome to maintain good performance. Security See: https://github.com/WICG/nav-speculation/blob/main/no-vary-search-security-privacy-questionnaire.md WebView application risks Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications? We are closely working with Android WebView team, and the broader prerender feature is gated through new AwSettings API (currently @RequiresOptIn) so there's zero risk that it will break existing WebView apps. Debuggability None Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)? Yes Is this feature fully tested by web-platform-tests <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md> ? Yes https://wpt.fyi/results/speculation-rules/prerender?label=experimental&label=master&aligned (The test files starting with no-vary-search) Flag name on chrome://flags None Finch feature name Prerender2NoVarySearch Requires code in //chrome? False Estimated milestones Shipping on desktop 127 Shipping on Android 127 Shipping on WebView 127 Anticipated spec changes Open questions about a feature may be a source of future web compat or interop issues. Please list open issues (e.g. links to known github issues in the project for the feature specification) whose resolution may introduce web compat/interop risk (e.g., changing to naming or structure of the API in a non-backward-compatible way). None Link to entry on the Chrome Platform Status https://chromestatus.com/feature/5190922953555968?gate=5148879099265024 Links to previous Intent discussions Intent to prototype: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CA%2B7y87rgssbBecLSY5fz03ATcAAjgy%3DjY322w_2roQdsehP4Dg%40mail.gmail.com This intent message was generated by Chrome Platform Status <https://chromestatus.com/>. -- You received this message because you are subscribed to the Google Groups "blink-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to blink-dev+unsubscr...@chromium.org. To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAHaAqYJphk8wg8yLr-VFe2QJDZ4N%3D8Z%2BBAs9VL5scY-brTmRTg%40mail.gmail.com.
