JWT Decoder & Encoder
Decode, verify, and build JWT tokens — entirely in your browser
Paste a JSON Web Token to instantly decode its header and payload, with pretty-printed timestamps and standard-claim tooltips. Verify HS256/HS384/HS512 signatures with your secret, or switch to Encode mode to build and sign new tokens. Everything runs client-side using the Web Crypto API — no token is ever sent to a server.
Enter the HMAC secret to verify the signature. Verification runs entirely in your browser.
Paste a JWT to decode it
Header, payload, and signature are decoded instantly in your browser — nothing is sent to a server.
Related developer tools
Try These Examples
Basic User Token (HS256)
A simple user authentication token with standard claims
Token (truncated):
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJ1c2VyXzEyMyI…Contains sub, name, email, iat, exp claims
Expired Token
A token with an exp claim in the past — demonstrates expiry warning
Token (truncated):
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODk…Shows the "Token Expired" badge in action
Admin Role Token (HS512)
An authorization token with role claims using HS512
Token (truncated):
eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJ1c2VyXzQ1NiI…Demonstrates array claims and HS512 algorithm
What is a JSON Web Token?
A JSON Web Token (JWT) is an open standard (RFC 7519) that defines a compact, self-contained way to securely transmit information between parties as a JSON object. JWTs are commonly used for authentication and authorization in modern web applications and APIs.
Unlike traditional session tokens, a JWT carries all the information needed to verify the user's identity directly in the token — no database lookup required. This makes them ideal for stateless, distributed systems.
Common Use Cases
• Authentication — verify user identity after login
• Authorization — determine what a user is allowed to do
• Information exchange — securely transmit claims between services
• Single Sign-On (SSO) — share authentication across multiple services
Frequently Asked Questions
Common questions about JWT tokens, signature verification, and token security.