# What are User-Agent Client Hints? | SoftGlaze Browser glossary

> User-Agent Client Hints describe the browser in Sec-CH-UA headers. How they work, which are sent by default, and why they must match the user agent.

- Canonical URL: https://browser.softglaze.com/glossary/client-hints
- Last updated 2026-11-07

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[Fingerprinting](https://browser.softglaze.com/glossary?category=fingerprinting)

## User-Agent Client Hints

Also called Client Hints, UA-CH, Sec-CH-UA, navigator.userAgentData, high entropy values

Definition

User-Agent Client Hints are a newer way for a browser to describe itself: a short brand and version list sent in Sec-CH-UA headers, with more detail, such as the platform version, architecture and full version, given only when a site asks for it.

Last updated 7 November 2026

### 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.

### Sources

1.  [User-Agent Client Hints API](https://developer.mozilla.org/en-US/docs/Web/API/User-Agent_Client_Hints_API) MDN Web Docs
2.  [User-Agent Client Hints (draft specification)](https://wicg.github.io/ua-client-hints/) WICG

Outside sources were checked in November 2026. Browsers, standards and vendors' pages change, so details that depend on them are as of that month.

### Related terms

-   [User agent](https://browser.softglaze.com/glossary/user-agent) A user agent string is the line of text a browser sends with every request, and shows to scripts, naming the browser, its version, the rendering engine and the operating system.
-   [Chromium](https://browser.softglaze.com/glossary/chromium) Chromium is the open-source browser project that Google Chrome, Microsoft Edge, Brave, Opera, Vivaldi and many other browsers are built on.
-   [TLS fingerprint (JA3 and JA4)](https://browser.softglaze.com/glossary/tls-fingerprint) A TLS fingerprint is a short summary of how a client opens an encrypted connection (the TLS version, cipher suites and extensions in its first message) that identifies the software making the connection, whatever its user agent says.
-   [Browser fingerprint](https://browser.softglaze.com/glossary/browser-fingerprint) A browser fingerprint is the combination of values a website can read from your browser and device without storing anything, such as the user agent, screen size, time zone, fonts and graphics card, which together can tell one browser from another.

### Read more on this site

-   [Docs: engines](https://browser.softglaze.com/docs/profiles#engines)
-   [Fingerprint management: OS and brand](https://browser.softglaze.com/features/fingerprint-management#os-and-brand)

### See it in SoftGlaze Browser

Separate profiles, each with its own cookies, device values and proxy, on Windows. Try the app's screens in your browser first, or start the free trial; no card needed.

[Download for Windows](https://browser.softglaze.com/download) [Try the demo](https://browser.softglaze.com/demo) [All terms](https://browser.softglaze.com/glossary)