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JWT Decoder & Encoder

Decode, verify, and encode JSON Web Tokens (JWT) instantly in your browser

Interactive tool

JWT input

Result

Run decode, verify, or encode to see header, payload, and token output here.

What is a JWT?

JWT (JSON Web Token) is a compact, URL-safe token format used for securely transmitting information between parties as a JSON object. It consists of three parts: header, payload, and signature. JWTs are commonly used for authentication and information exchange in web applications.

How to Use This JWT Tool

  1. 1Choose an action: Decode (view contents), Verify (check signature), or Encode (create new JWT)
  2. 2For Decode: paste your JWT token
  3. 3For Verify: paste JWT and enter the secret key
  4. 4For Encode: enter payload data and secret key
  5. 5View the decoded header, payload, and verification status
What you get

Key features

Decode JWT

View header and payload contents without verification

Verify Signature

Validate JWT signature with secret key

Encode JWT

Create new signed JWTs with custom payload

Multiple Algorithms

Support for HS256, HS384, and HS512

Expiration Time

Set token expiration when encoding

JSON Formatting

Pretty print header and payload for readability

100% Private

All JWT processing happens locally in your browser

Free Forever

No registration, no limits, completely free

Why Use JWT?

JWTs are self-contained tokens that can be verified without querying a database, making them efficient for authentication in distributed systems. They are stateless, portable, and can carry custom claims. The signature ensures the token has not been tampered with, while the payload remains readable for quick access to user information.

Common use cases

  • User authentication and session management
  • API authorization and access control
  • Single sign on (SSO) across domains
  • Secure information exchange between services
  • Mobile app authentication
  • Microservices authorization

JWT Structure

  • Header: Contains token type (JWT) and signing algorithm
  • Payload: Contains claims (user data and metadata)
  • Signature: Ensures token integrity and authenticity

JWT Security Best Practices

Always use HTTPS to prevent token interception. Use strong, random secrets for signing. Set appropriate expiration times (short for access tokens). Never store sensitive data in JWT payloads as they are readable. Validate tokens on every request. Use refresh tokens for long-lived sessions.

Pro tips

Tips & best practices

JWT is not encryption

JWT payload is Base64 encoded, not encrypted. Anyone can decode and read it. Use it for public claims only.

Keep secrets secret

Never expose your JWT secret. Use environment variables and keep secrets server-side only.

Set expiration times

Always set exp claim to limit token validity. Short lived tokens (15min-1h) are more secure.

Validate on every request

Always verify JWT signature and check expiration on the server before trusting the token.

Use RS256 for production

Consider using asymmetric algorithms (RS256) instead of HS256 for better security in production.

Built for trust

Privacy & security

This JWT tool runs entirely in your web browser. Your tokens and secrets are never uploaded to any server, stored in any database, or transmitted anywhere. All decoding, encoding, and verification happens locally on your device. It is 100% private and secure.

Related tools

Frequently Asked Questions

What is a JWT?

A JSON Web Token (JWT) is a compact, URL-safe token with three parts: header, payload, and signature. It is often used to carry identity and claims between a client and server after sign-in.

Is the JWT payload encrypted?

No. The header and payload are Base64URL-encoded JSON, not encrypted. Anyone who has the token can read those parts. Do not put secrets in the payload; use HTTPS and short-lived tokens for sensitive workflows.

What algorithms does this tool support?

Encoding and verification support symmetric HMAC: HS256, HS384, and HS512. Decode only parses the token and does not check the signature.

Does my token leave my browser?

No. Decode, verify, and encode all run locally in your browser using JavaScript. Tokens and secrets are not sent to Zap.Tools servers.

When should I use verify instead of decode?

Use decode to inspect header and payload quickly. Use verify when you have the signing secret and need to confirm the token was not tampered with and is cryptographically valid.