Decode a JSON Web Token (JWT) instantly to view its header and payload in a readable JSON format. Runs fully in your browser for secure debugging and token inspection. Supported JWT algorithms: HS256, HS384, HS512, RS256, RS512, PS256.
Decode JWT Token Online
100% Client-Side Execution. No Data Sent to Server Secure
Decode a JSON Web Token to instantly view its header and payload. No secret or private key is required.
Header Copy
Payload Copy
Signature
Header Validation
Claim Validation
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Validate a JWT by verifying its signature and checking registered claims such as expiration and not-before.
Generate a signed JWT using custom headers and claims for testing authentication and authorization flows.
All processing happens locally using the browser’s WebCrypto API. Your tokens and keys are never sent to any server, making this tool safe for debugging production JWTs.
What Is a JSON Web Token?
A JSON Web Token (JWT) is a compact, URL-safe means of representing claims to be transferred between two parties. It consists of three parts: Header, Payload (claims), and Signature.
JWTs are widely used for API authentication, single sign-on (SSO), and securely transmitting information between client and server.
A JWT consists of three parts separated by dots: the header, the payload, and the signature. While the signature ensures integrity, the header and payload can be decoded without verification.
How JWT Decoding Works
JWT decoding converts the Base64URL-encoded header and payload into readable JSON. This allows developers to inspect token metadata and registered claims such as issuer, subject, and expiration time.
Decoding does not verify token authenticity. To ensure a token has not been tampered with, signature verification should be performed using a JWT validator.
When Should You Use a JWT Decoder?
- Debug authentication and authorization issues
- Inspect JWT claims during API development
- Understand tokens issued by identity providers
- Verify token structure before signature validation
Is JWT Decoding Secure?
JWT decoding is safe when performed in a trusted environment. This tool processes tokens entirely in your browser and does not transmit any data externally.
For cryptographic validation, combine decoding with signature verification and encryption tools such as RSA encryption or ECC key verification.
Use Cases
A JWT Decoder is commonly used during development and debugging to inspect the contents of a token without performing cryptographic verification.
- Check tokens returned by OAuth 2.0 providers such as Okta, Auth0, or Keycloak
- Debug HTTP 401 and 403 responses from secured APIs
- Analyse token structure differences across staging and production environments
- Inspect custom private claims added by your application
Security best-practice hints
- Decoding a JWT does not guarantee it is valid - always verify the signature.
- Do not trust sensitive claims unless the token is verified using RS256/RS512 or PS256.
- Keep your secrets and private keys secure - only share public keys for verification.
Tool Capabilities
- Decodes Base64URL-encoded JWT header and payload
- Displays claims in readable JSON format
- Supports standard and custom JWT claims
- Runs entirely in the browser with no server interaction
Key Terminologies
- JWT - A compact token format used for secure information exchange
- Header - Contains token type and signing algorithm
- Payload - Stores registered and custom claims
- Base64URL - Encoding format used by JWT components
Frequently Asked Questions (FAQ)
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