User Agent by SandVPN

Some sites still refuse Firefox. SandAgent lets you present a different
browser identity — and, unlike most user-agent switchers, it keeps every
related value consistent with the one you chose.

EVERYTHING FROM ONE SOURCE
The User-Agent header and navigator.userAgent are produced from the same
value, so they cannot contradict each other. The same goes for the platform,
appVersion, vendor, the Sec-CH-UA client hints and navigator.userAgentData.
A mismatch between them is the first thing any detection script looks for,
and it is the flaw most user-agent switchers ship with.

TWO KINDS OF PROFILE, CLEARLY LABELLED
Stealth presents you as a different Firefox — a different version, or a
different operating system. Because the engine really is Firefox, nothing
in the environment can contradict the disguise.
Compatibility presents you as Chrome, Edge or Safari. This unblocks sites
that read the User-Agent string, which is what most of them do.

WHAT IT DOES NOT DO
Compatibility profiles do not fool bot-detection systems, and the add-on
says so in its own interface. The TLS and HTTP/2 fingerprints are produced
by Firefox's network stack, below any extension API, and services like
Cloudflare cross-check them against the announced User-Agent. No browser
extension can change that. If you want a quiet browsing experience on
protected sites, the honest answer is to stay on a Firefox profile.

THE RIGHT PROFILE, SITE BY SITE
Keep your real Firefox everywhere and put on a Chrome profile only where you
need it. A rule covers a domain and all its subdomains, and both the headers
and the JavaScript follow it.

YOUR OWN USER-AGENT
Paste any string. SandAgent uses it verbatim and derives the matching values
from it. If it cannot read the string, it says so instead of guessing — no
bundled list of user agents, so nothing ever goes stale.

BUILT-IN DIAGNOSTIC
One click replays, on the current page, the checks a fingerprinting script
would run. It reports what is coherent, what is not, and which engine-level
tells remain out of reach of any extension.

PRIVATE BY DESIGN
No account. No analytics. No telemetry. No data collection of any kind.
SandAgent makes no network requests of its own; it only modifies requests
your browser was already making. Available in English and French.