JWT Encoder & Decoder Online – Secure JSON Web Token Tool

Decode, encode, and inspect JWT tokens online with a secure, browser-based JWT encoder and decoder. No uploads. No backend. 100% privacy-first.🔒 All processing happens in your browser. Your data never leaves your device.

Timestamps:
iat: 18/1/2018, 7:00:22 am
Warning: Never use this with production secrets. This tool is for development and debugging only.

About JWT Tokens

JSON Web Tokens (JWT) are a compact and URL-safe standard for securely transmitting claims between systems. A JWT consists of three parts separated by dots:

  • Header: Contains metadata about the token (algorithm, type)
  • Payload: Contains the claims (user data, permissions, timestamps)
  • Signature: Ensures token integrity and authenticity

Common Claims: iss (issuer),sub (subject),aud (audience),exp (expiration),iat (issued at)

Disclaimer: This tool is intended for development, debugging, and educational purposes only and does not replace production-grade security validation systems. All processing happens locally in your browser—no data is transmitted to any server.

How to Use

  1. 1Select Decode or Encode mode
  2. 2For Decode: Paste your JWT token to automatically decode it
  3. 3For Encode: Edit the header and payload JSON, then copy the generated token
  4. 4Optionally enter a secret to verify/sign the token (HS256 only)
  5. 5View decoded claims including timestamps in human-readable format

Example

Input:

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c

Output:

Header: {"alg":"HS256","typ":"JWT"}, Payload: {"sub":"1234567890","name":"John Doe","iat":1516239022}

Frequently Asked Questions

What is a JWT token?

A JSON Web Token is a compact, self-contained token used to securely transmit information between parties as a JSON object.

Is my JWT data safe here?

Yes. All processing happens locally in your browser. No data is sent to any server.

Can I verify JWT signatures against real servers?

No. This tool validates structure and encoding only and does not communicate with external authentication systems.

Which algorithms are supported?

Currently only HS256 (HMAC SHA-256) is supported for browser-based signing. Other algorithms like RS256 and ES256 require additional cryptographic setup.

Should I paste production secrets here?

Avoid pasting real production secrets unless you fully trust your environment. This tool is intended for development and debugging purposes.