Document that display-based capture is unavailable on headless - #538
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Document that display-based capture is unavailable on headless#538courtney918 wants to merge 1 commit into
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Live view and replays are already documented as headless limitations, but the screenshot telemetry category and computer-controls screenshots share the same display dependency without saying so. Name the common cause on the headless page, warn on the screenshot category row, and point at the framework-level screenshot call that does work without a display. Also make replay opt-in explicit, so "headful supports replays" isn't read as "headful records automatically."
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Summary
Live view and replays are already documented as unavailable on headless. Two other features share the exact same display dependency and don't say so anywhere:
screenshottelemetry category, described as "Periodic screenshots of the session" with no mode caveatBoth can be enabled on a headless session and accepted, but neither can capture the page — there's no display to capture. Someone debugging a headless session reaches for the screenshot category precisely because it looks like the thing that would help, gets nothing back, and has no way to find out why.
This names the common cause once on the headless page, warns on the category row, and points at the framework-level screenshot call that does work headless (Playwright's
page.screenshot()renders in the page, so it needs no display).Separately:
introduction/create.mdxdescribes headful as supporting "live view, replays, and better stealth," which reads as though headful records automatically. It doesn't — recording is an explicitreplays.start()/replays.stop()pair. Someone who switches to headful expecting a recording gets none and reasonably concludes headful didn't solve their problem. Made the opt-in explicit there and on the replays page.Changes
browsers/headless.mdxbrowsers/telemetry/categories.mdxscreenshotrow headful-only; added a Warning explaining why and what to use insteadbrowsers/replays.mdxintroduction/create.mdxNotes
Docs-only, no code changes. The wording deliberately says the category "can't capture the page" and "won't give you usable frames" rather than claiming it emits nothing — the capture path is display-based either way, but I didn't verify whether it errors out or emits an empty frame, and the docs shouldn't assert more than that.