Language Tag Syntax Checker
Check browser-supported language-tag syntax and canonical spelling while identifying private-use tags separately.
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How to use Language Tag Syntax Checker
Normalize common locale tags and see whether this browser accepts them. This deliberately limited checker does not bundle the complete IANA registry or reject every valid-but-unsupported BCP47 spelling.
- Enter input.
- Choose the settings for language tag syntax checker, then run the tool.
- Review the result and any limitations before copying or downloading it.
Good to know
- No complete registered-subtag, grandfathered-tag, deprecation or preferred-value database is bundled.
- Intl rejection alone does not prove a tag invalid under all of BCP47. A tag does not identify the actual document language.
- Processing is local. Output is limited to 1,000,000 text characters unless a stricter file limit is stated.
Common questions
Does this validate every registered BCP47 tag?
No. It exposes browser Intl syntax/canonicalization and a separate private-use grammar only.
Is this input sent to a server?
No. The application processes this input inside your browser tab and does not save it to persistent storage.
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