Base64 Validator

What Base64 Validator does

The Base64 Validator checks whether a string is correctly encoded Base64 — the right character set, proper padding with '=', and a length that's a multiple of 4. It's a quick way to catch corrupted or truncated encoded data before you try to decode it, and it runs entirely in your browser with nothing uploaded to a server.

How to use Base64 Validator

1. Paste the Base64 string you want to check
2. The tool validates it automatically as you type
3. Review whether it's valid, and the specific reason if it isn't (bad character, wrong padding, wrong length)
4. Fix the string and re-check, or decode it once it passes

Who should use it

Made for developers. Typical uses:

• Confirming an API response's Base64-encoded field wasn't truncated during a copy-paste
• Checking a data URI (data:image/png;base64,...) is well-formed before embedding it in CSS or HTML
• Verifying a JWT header or payload segment decodes cleanly before debugging an authentication issue

Frequently asked questions

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