Intent to Experiment: Viewport-height client hint
Max Curran
Contact emails
curr...@chromium.org, ryan...@chromium.org
Explainer
https://github.com/WICG/responsive-image-client-hints/blob/master/Viewport-Height-Explainer.md
Specification
https://wicg.github.io/responsive-image-client-hints/#sec-ch-viewport-height
Summary
Currently, Responsive Image Client Hints provide a way for origins to obtain the viewport’s width. However, no such attribute exists for viewport height. We’ve observed that to optimize the loading of content that appears in viewport, it is essential for the origins to adapt HTML response based on viewport height.
Blink component
TAG review
https://github.com/w3ctag/design-reviews/issues/615
TAG review status
Issues addressed
Link to origin trial feedback summary
https://github.com/WICG/responsive-image-client-hints/issues
Risks
Interoperability and Compatibility
Gecko: No signal (https://github.com/mozilla/standards-positions/issues/79)
WebKit: Negative (https://lists.webkit.org/pipermail/webkit-dev/2020-November/031576.html) Likely to be neutral based on discussion in https://github.com/mozilla/standards-positions/issues/79
Web developers: No signals
Other signals:
Activation
None
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?
Goals for experimentation
Client hints opt-ins from origins are session-sticky which makes it difficult to experiment with using origin trials since origin trials operate at document-level. We plan to run an A/B experiment using Chrome’s field trial infrastructure. Our plan is to enable the feature for at most 1% users to collect metrics, and ship this feature only if it shows performance improvement for origins that choose to use this feature.
Reason this experiment is being extended
Due to Chrome approvals taking longer than expected, and partners still needing to implement how to use the client hint, we have not been able to experiment yet. We would like to extend the origin trial from M101 to M104.
Ongoing technical constraints
Debuggability
N/A
Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?
Yes
Is this feature fully tested by web-platform-tests?
Yes
Flag name
kViewportHeightClientHintHeader
Requires code in //chrome?
False
Tracking bug
https://bugs.chromium.org/p/chromium/issues/detail?id=1184863
Launch bug
https://bugs.chromium.org/p/chromium/issues/detail?id=1184862
Estimated milestones
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5646861215989760
Links to previous Intent discussions
Intent to Experiment: https://groups.google.com/a/chromium.org/g/blink-dev/c/Q2wcqY2UyNs/m/rPePdX_NBwAJ
This intent message was generated by Chrome Platform Status.
Yoav Weiss
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