v147 · origin trial · prerendering

Compatibility Lab

A live compatibility lab for the Chrome 147 cross-origin iframe prerender path: browser capability probes, top-level and iframe Supports-Loading-Mode gates, activation timing, and fallback decisions when the current browser cannot actually prerender the page.

Runtime support is probed below. If this browser does not expose the prerender APIs or the Chrome 147 origin-trial behavior, the lab still models the server-header decisions and shows the fallback path a production page should take.

Live browser probes

Eligibility builder

normal navigation

Top-level prerendered page response The prerender-cross-origin-frames token is the top-level opt-in that lets cross-origin iframes navigate while the page is prerendering.

Iframe origin relationship Same-origin iframes are not gated by this new cross-origin opt-in. Cross-origin frames take the compatibility path below.

Iframe response loading mode A cross-origin iframe response must opt into being used while prerendered; credentialed-prerender is the supported token in this path.

Failure or deferral case These cases surface the spec's fallback space: wait for activation, block scripts, or discard the prerender candidate.

Use blocked-until-activation script mode Models prerender_until_script behavior: side effects are delayed until prerenderingchange instead of running in the hidden prerender context.

Decision matrix

checking

Request trace

Activation and fallback log

Implementation checkpoints

document.prerendering is true only while the page is hidden in a prerendering navigable; listen for prerenderingchange before running analytics, autoplay, prompts, or other activation-sensitive work.
PerformanceNavigationTiming.activationStart > 0 identifies a page that was prerendered and then activated. Normal navigations keep it at zero or omit the field.
The top-level prerendered document uses Supports-Loading-Mode: prerender-cross-origin-frames to allow cross-origin iframe navigation while prerendering.
The cross-origin iframe response needs a supported loading-mode opt-in such as credentialed-prerender; unsupported or missing tokens move the frame to the fallback path.

references

implementation reference

Need the exact API surface, compatibility boundaries, errors, lifecycle, and source links? Read the matching gendn reference ↗