Per-Site User-Agent by Patrick Wozniak

Per-Site User-Agent chooses the user agent your browser sends, website by website. Appear as Chrome on the one site that misbehaves, stay yourself everywhere else.

Some sites detect the browser in JavaScript, not only in the request header. That is why this extension rewrites both:

• HTTP headers: User-Agent, and for Chrome profiles also Sec-CH-UA, Sec-CH-UA-Mobile, Sec-CH-UA-Platform.
• JavaScript: navigator.userAgent, userAgentData (including getHighEntropyValues()), appVersion, platform, vendor, productSub; Firefox-only properties such as oscpu are removed where needed.

Rules

• Match by domain and optional path, with wildcards: app.paper.design, *.paper.design, github.com/user/*.
• The most specific rule wins. A "browser default" exception can override a broader rule.
• Live preview while typing: what the pattern means, which open tabs match, spelling hints.
• A tester shows which rule applies to any URL.

User agents

• Current presets for common browser and OS combinations, plus your own named, reusable custom user agents.
• Presets can be refreshed from a public list. The fetch happens only when you click the update button.

Good to know

• Toolbar popup for the current site; full settings page with light, dark or forced theme.
• Everything is stored locally. The extension collects no data and sends nothing anywhere, except the optional, click-triggered preset update.
• Works in Firefox and Firefox-based browsers such as Zen.
• English and German interface.

Feedback is welcome — if a site still detects your browser, tell me which rule you used.