Browser Language Detector
See every language your browser sends in the Accept-Language header, with locale details.
How to use this tool
- Open this page — it runs instantly in your browser, no signup or install.
- Allow any permission prompt if asked; everything stays on your device.
- Use the on-screen controls — results update live.
See every language your browser sends in the Accept-Language header, with locale details.
How it works
The Browser Language Detector reads the navigator.language and navigator.languages properties your browser exposes to JavaScript and displays every language code your browser sends to websites. These are the same values websites use to decide which language to show you by default.
The primary language is the first entry in the list and is typically the language you set when you configured your browser or OS. Additional languages are fallbacks that the browser will accept if content is not available in the primary language. Each entry is a BCP 47 language tag such as 'en-US', 'fr-FR', or 'zh-Hant-TW'.
This tool is useful for checking why a website defaults to the wrong language, for verifying that a browser profile is set up with the correct locale for testing, and for understanding what language information your browser leaks to every website you visit.
The values are read directly from browser JavaScript properties. No network request is needed.
Worked example
Check why a website displays in the wrong language
- Open the Browser Language Detector.
- Note the primary language shown (e.g. 'de-DE').
- Compare it to the language the website is displaying.
- If the website is using the language listed here, the issue is your browser language setting, not the website.
- Change the browser language in OS or browser settings and reload to verify.
Identified whether the wrong-language display is caused by the browser's language preference or by a bug in the website's locale detection.
Common mistakes to avoid
- Changing the browser language in settings but not restarting the browser — some browsers require a restart for the change to take full effect.
- Expecting navigator.language to return the page language — it returns the browser's preferred language, not the language of the page currently open.
- Confusing the browser language setting with the keyboard input language — these are independent settings that do not affect each other.
Key terms
- BCP 47 language tag
- A standardised code that identifies a language and optional region, script, or variant (e.g. 'en-US' for American English, 'zh-Hant' for Traditional Chinese).
- navigator.language
- A browser property that returns the primary language tag the browser is configured to use.
- Accept-Language header
- An HTTP request header browsers send to servers listing the user's preferred languages in priority order, mirroring navigator.languages.
Frequently asked questions
- What is Accept-Language?
- It is an HTTP request header your browser sends to servers listing your preferred languages in order, e.g. en-US,en;q=0.9,fr;q=0.8.
- Can I change my browser language?
- Yes — in Chrome go to Settings → Languages. In Firefox go to Settings → General → Language. Changes take effect on the next request.