HTTP Client Hints

Client Hints let a server request selected information about a browser, device, network, or user preference.

Use Accept-CH to opt into hints, vary responses carefully, and request only information the application needs. Client hints can expose device and preference data.

httpbrowserprivacyperformance

Reference (http)

Accept-CH: Sec-CH-UA-Mobile, Sec-CH-Prefers-Color-Scheme
Vary: Sec-CH-UA-Mobile

Use Accept-CH to opt into hints, vary responses carefully, and request only information the application needs. Client hints can expose device and preference data.

Common mistakes

Collecting every available hint or forgetting that hint-dependent responses need cache variation.

Sources

MDN HTTP Reference