How to use this tool
- Enter your values or try the example.
- Run the tool and check the result.
- Save the result where a download is available.
Supported features & limits
Checks HTML alternate links for language-tag syntax, duplicate language tags, absolute URLs and a self-reference. Does not fetch target pages or verify reciprocal links, redirects or Google indexing. Maximum 100 KB.
What happens to my files?
Your browser reads the file locally. File contents are not sent to our server. Closing or resetting this page clears the working result. Downloaded copies remain on your device.
Maintained by Roman Zmazhenko. Updated 1 November 2026.