Sec-CH-Prefers-Reduced-Motion User Preference Media Features Client Hints Header

Category: Network / Connectivity
Type: New or changed feature
Status: Enabled by default (Chrome 108)
Intent stage: None

Breaking change: No
Enterprise impact: None
Spec maturity: Incubation
Web Platform Tests: No

WPT details: https://wpt.fyi/results/client-hints

Summary

User Preference Media Features Client Hints Header defines a set of HTTP Client Hints headers around user preference media features as defined by Media Queries Level 5. If used as Critical Client Hints, these headers allow servers to make smart choices regarding, e.g., CSS inlining. Sec-CH-Prefers-Reduced-Motion reflects the user's prefers-reduced-motion preference.

Standards & signals

Specification: https://wicg.github.io/user-preference-media-features-headers/#sec-ch-prefers-color-scheme
Firefox: No signal
Safari: N/A
Web developers: Positive — (WICG proposal Issue: https://github.com/WICG/proposals/issues/30 with feedback from developers working for Facebook and Magento. Twitter: https://twitter.com/kilianvalkhof/status/1392404416335056896. The proposal was initially discussed in https://github.com/w3c/csswg-drafts/issues/4162 and received positive feedback via 16 Likes and 3 supportive comments: https://github.com/w3c/csswg-drafts/issues/4162#issuecomment-621047333, https://github.com/w3c/csswg-drafts/issues/4162#issuecomment-631400330, and https://github.com/w3c/csswg-drafts/issues/4162#issuecomment-645742958). Google Search is interested in this header, too.
Tracking bug: https://crbug.com/1361871

Ecosystem

Web Platform Tests: https://wpt.fyi/results/?q=client-hints
Chrome Platform Showcase: https://chrome-platform-showcase.paulkinlan-ea.deno.net/features
GenDN reference: https://gendn.paulkinlan-ea.deno.net/features
chrome.dev demos search: https://www.google.com/search?q=site%3Achrome.dev+Sec-CH-Prefers-Reduced-Motion%20User%20Preference%20Media%20Features%20Client%20Hints%20Header
MDN Web Docs: https://developer.mozilla.org/en-US/search?q=Sec-CH-Prefers-Reduced-Motion%20User%20Preference%20Media%20Features%20Client%20Hints%20Header
Baseline status: https://webstatus.dev/?q=Sec-CH-Prefers-Reduced-Motion%20User%20Preference%20Media%20Features%20Client%20Hints%20Header

Samples: https://sec-ch-prefers-reduced-motion.glitch.me/

Explainers: https://github.com/wicg/user-preference-media-features-headers/blob/main/README.md

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