About This Tool
What is JWT Encoder / Decoder?
A tool for encoding and decoding JWT (JSON Web Tokens). JWT is a widely used token format for web authentication and information exchange. You can separate and inspect the header, payload, and signature of a token.
How to Use
- In decode mode, paste a JWT token string to automatically separate the header and payload.
- In encode mode, enter header and payload in JSON format.
- Optionally enter a secret key to generate a signed token.
- Copy the result for your use.
Key Features
- JWT token decoding and structure analysis
- JWT token encoding (with or without signature)
- Separate display of header, payload, and signature
- Formatted JSON output for readability
Tips
- A JWT consists of three parts separated by dots: Header.Payload.Signature.
- JWT payloads are only Base64-encoded, not encrypted โ never put sensitive information in them.
- Check standard claims like expiration time (exp) and issued at (iat) to validate tokens.
JWT Encoder / Decoder
Encode or decode JWT tokens
Frequently Asked Questions
Is it safe to decode JWT tokens in the browser?โผ
Yes. JWT payloads are only Base64-encoded, not encrypted โ anyone with the token can read the payload. Decoding in the browser is perfectly safe and is how JWTs are designed to be used. The signature ensures the token hasn't been tampered with, but the content is intentionally readable.
What are the common JWT claims I should check?โผ
Key standard claims: 'exp' (expiration time โ reject if expired), 'iat' (issued at โ when the token was created), 'nbf' (not before โ token not valid before this time), 'sub' (subject โ usually user ID), 'iss' (issuer โ who created the token), 'aud' (audience โ intended recipient).
What is the difference between JWT and session-based authentication?โผ
Sessions store state on the server (session ID in cookie, data in server memory/database). JWTs are stateless โ all user data is in the token itself. JWTs scale better (no server-side storage) but can't be easily revoked. Sessions offer simpler revocation but require shared session storage in distributed systems.
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