JWT Decoder
Decode JSON Web Tokens securely without server uploads.
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Note: This tool only decodes the token payload client-side. It does not cryptographically verify the signature against a secret key.
What is this tool?
Decodes JSON Web Tokens (JWT) to reveal the unencrypted header and payload claims without requiring the signing secret.
How to decode a JWT
- Paste your encoded JSON Web Token into the input field.
- The tool instantly parses the Base64Url-encoded segments.
- View the formatted JSON header and payload in the output panels.
- Inspect standard claims like expiration (exp) and issued-at (iat) times.
Key Features
- Instant client-side Base64Url decoding
- Pretty-printed JSON formatting
- Automatic timestamp conversion for standard JWT claims
- Handles invalid or malformed tokens gracefully
Frequently Asked Questions
Can this tool verify if a JWT is legitimate?
No. This tool only decodes the unencrypted portions (Header and Payload). Verifying the token's authenticity requires the secret signing key, which is intentionally not requested here.
Why is the payload readable without a password?
Standard JWTs are digitally signed, but not encrypted. The payload is simply Base64Url encoded, meaning anyone with the token can easily read the data inside it.
Privacy First
Decoding occurs entirely via client-side JavaScript string manipulation. Your sensitive tokens are never sent to a server for processing.