LGTM to experiment M144-M149 inclusive (6 milestones, rather than the 
requested 7)

Please change the chrome status entry to indicate the above.

On Tuesday, January 13, 2026 at 7:28:01 AM UTC+1 Chromestatus wrote:

> *Contact emails*
> [email protected]
>
> *Explainer*
> https://github.com/WICG/nav-speculation/blob/main/prerender-until-script.md
>
> *Specification*
>
> https://wicg.github.io/nav-speculation/prerendering.html#speculation-rule-set-prerender_until_script-rules
>  
>
> *Design docs*
>
>
> https://docs.google.com/document/d/18Ny-OJ5kfyxkZ8h73OGigk8B3gDnoxjH34RVcvSo5Do/edit?tab=t.szm4nrdsfrjv
>
> *Summary*
> This extends speculation rules to introduce a new action called 
> prerender_until_script. It is designed as an intermediate option between 
> the existing prefetch (which only fetches the main document) and prerender 
> (which fully renders the page and runs all scripts). This new action will 
> fetch and parse a page, discover and download its subresources like images 
> and stylesheets, but will pause all script execution. When the user 
> navigates to the page, it activates, and all the deferred scripts are then 
> executed in order. This allows for a near-instant page load for 
> content-heavy sites without the performance cost or side effects of running 
> analytics or third-party scripts prematurely. 
>
> *Blink component*
> Internals>Preload>Prerender 
> <https://issues.chromium.org/issues?q=customfield1222907:%22Internals%3EPreload%3EPrerender%22>
>
> *Web Feature ID*
> speculation-rules <https://webstatus.dev/features/speculation-rules> 
>
> *Search tags*
> speculationrules <http:///features#tags:speculationrules>, prerendering 
> <http:///features#tags:prerendering>, prefetch 
> <http:///features#tags:prefetch>, nostateprefetch 
> <http:///features#tags:nostateprefetch>
>
> *TAG review*
> https://github.com/w3ctag/design-reviews/issues/1183 
>
> *TAG review status*
> Not applicable
>
> *Origin Trial documentation link*
> https://github.com/WICG/nav-speculation/blob/main/prerender-until-script.md 
>
> *Risks*
>
>
> *Interoperability and Compatibility*
> Other browsers do not implement this feature yet, but if should be safe 
> because: 1. it is an optimization, so it should be no-op on other browsers 
> 2. other browsers do not implement any of speculationrule actions yet. 
>
> *Gecko*: No signal
>
> *WebKit*: No signal
>
> *Web developers*: Positive (
> https://github.com/WICG/nav-speculation/issues/305) Web developers 
> proposed that UA should implement an intermediate option between the 
> existing prefetch and prerender actions.
>
> *Other signals*:
>
> *Ergonomics*
> no
>
> *Activation*
> No. Developers should be able to easily try this feature by changing 
> "prerender" to "prerender_until_script" following the explainer. 
>
> *Security*
> It should be as safe as prerender action, as it pauses JavaScript 
> execution during prerendering. One potential risk is the inline event 
> handlers. inline event handlers will be executed normally during 
> prerendering, it seems risky but we find websites usually put inline 
> scripts before defining a inline event handler, and the inline script will 
> make the parser be paused, therefore user agent has no chance to execute 
> the inline event handlers. So, we think is is a low possibility risk, and 
> would like to confirm with Origin Trial.
>
> *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? 
> *No information provided* 
>
>
> *Goals for experimentation*
> *No information provided*
>
> *Ongoing technical constraints*
> We assume it is ok not to handle inline event handlers differently as for 
> now most pages put <script> tag before inline event handlers. But if it 
> happens, we need to refine the inline event handlers' execution logic.
>
> *Debuggability*
> As well as other speculationrule features, this feature shows its current 
> status on devtools. 
>
> *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 
>
>
> *Flag name on about://flags*
> prerender-until-script 
>
> *Finch feature name*
> PrerenderUntilScript 
>
> *Requires code in //chrome?*
> False
>
> *Tracking bug*
> https://issues.chromium.org/u/1/issues/428500219
>
> *Measurement*
> Blink.UseCounter.Features
>
> *Estimated milestones*
> Origin trial desktop first 144 
> Origin trial desktop last 150 
> DevTrial on desktop 144 
> Origin trial Android first 144 
> Origin trial Android last 150 
> DevTrial on Android 144 
> Origin trial WebView first 144 
> Origin trial WebView last 150 
>
> *Link to entry on the Chrome Platform Status*
> https://chromestatus.com/feature/6324676351623168?gate=5823668919861248
>
> *Links to previous Intent discussions*
> Intent to Prototype: 
> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/68f20f78.050a0220.29f70d.004e.GAE%40google.com
>
>
> This intent message was generated by Chrome Platform Status 
> <https://chromestatus.com>. 
>

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