User-Agent Client Hints

How it works

With every request, a Chromium-based browser sends three hints by default: Sec-CH-UA (a list of brands with major versions, such as Chromium and Google Chrome), Sec-CH-UA-Mobile and Sec-CH-UA-Platform. A site that wants more replies with an Accept-CH header, and the browser then sends the higher-detail hints: the full version list, the platform version, the CPU architecture and bitness, and the device model. Scripts get the same data from navigator.userAgentData, with getHighEntropyValues() for the detailed part.

Client Hints were introduced to let Chrome shrink the user agent string while still giving sites what they need when they ask. The brand list usually includes a deliberately meaningless entry, so sites don’t match on exact strings. As of November 2026, MDN’s compatibility data shows Firefox and Safari don’t support them, so a browser that claims to be Firefox and sends them is contradicting itself.

Why it matters when you run several accounts

Client Hints and the user agent describe the same browser twice, and they have to agree. A user agent that says Chrome 147 next to a Sec-CH-UA list that says 149, a Windows user agent with a Sec-CH-UA-Platform of macOS, or a Chrome user agent with no hints at all, are all contradictions a site can check in one line of code.

How SoftGlaze Browser handles it

The app keeps Client Hints switched on and sets each profile’s hint values with the rest of its identity, so the headers and navigator.userAgentData report the same brands, platform, platform version and model as the user agent. The full version of the Chromium and Google Chrome brands is the real version of the binary that runs, which is why the app downloads Chrome builds by version. Choosing a brand such as Edge or Opera changes the user agent token and the brand list together.