demo · v147

Policy Headers

Four Document Policy directives that now flow through to Dedicated Workers.

no-sync-xhr

Document-Policy: no-sync-xhr

Synchronous XMLHttpRequest is rejected. Helps eliminate the worst of jank.

js-profiling

Document-Policy: js-profiling

Required to use the JS Self-Profiling API. Without it, new Profiler({}) throws.

oversized-images

Document-Policy: oversized-images=2.0

Reject images that exceed their layout box by the given multiplier. Catches accidental hero-image bloat.

unsized-media

Document-Policy: unsized-media=?0

Reject <img>, <video>, <canvas> without intrinsic dimensions. CLS killer.

see also

scenario focus

Select a scenario to focus its rendered example and summary.

implementation reference

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