Base64URL Decoder
Base64URL Decoder
Decode Base64URL text into UTF-8 output.
InputsManual input36 charsAuto run
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Flow
- Validate Base64URL alphabet usage.
- Normalize to standard Base64 alphabet and padding.
- Decode normalized value into UTF-8 text.
Example
Worked example: decode JWT header segment
- 1 Input = eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9
- 2 Normalizer restores Base64 padding and alphabet.
- 3 Decoded output = {"alg":"HS256","typ":"JWT"}
The Base64URL segment is converted into readable JSON text.
How
- Paste Base64URL text in the input box.
- Run decode to normalize and decode the payload.
- Copy output text or review error messages for malformed input.
Cases
- Read JWT header and payload segments manually.
- Debug URL-safe encoded values from web apps.
- Validate whether Base64URL input decodes to UTF-8 text.
Avoid
- Feeding standard Base64 with slash and plus into Base64URL-specific logic.
- Expecting signature verification from decoded token segments.
- Ignoring malformed input warnings and using partial output.
FAQ
Can this decode JWT segments?
Yes, JWT header and payload segments are Base64URL and decode correctly in this tool.
Does this verify token signatures?
No, decoding only converts text and does not validate signatures.
Why does malformed input fail?
The decoder validates Base64URL character set and normalization requirements.
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