Jwt Parser

Free online tool. All processing is client-side. No signup needed.

How to Use the Jwt Parser

1. Enter your input values above
2. Results update automatically
3. Copy or download the output

What is a Jwt Parser?

A JWT Parser decodes and displays the contents of JSON Web Tokens — compact, URL-safe tokens used for authentication and information exchange between parties. JWTs are everywhere in modern web applications: they're how your browser proves to a server that you're logged in, how APIs authorize requests, and how single sign-on (SSO) systems share identity information. A JWT consists of three Base64-encoded parts separated by dots: the Header (algorithm and token type), the Payload (claims — who you are, when the token expires, permissions), and the Signature (cryptographically verifies the token hasn't been tampered with).

How Does It Work?

Paste a JWT token string (looks like: eyJhbG... .eyJzdWI... .SflKx...). The parser splits it at the dots, Base64-decodes the Header and Payload, and displays them in a readable, color-coded format. The Payload shows all claims: standard claims (iss, sub, aud, exp, iat), custom claims your application defines, and timestamps converted to human-readable dates. The Signature is shown but not verified — you need the secret key or public key for that.

Formula

JWT Structure: Header.Payload.Signature\n\nHeader (decoded):\n{\n  \

Who Uses This Tool?

• Developers debugging authentication issues by inspecting JWT contents
• Security engineers verifying token expiration and claim validity
• API developers testing whether JWTs contain expected claims
• System administrators troubleshooting SSO and OAuth flows
• Anyone understanding what information their JWT tokens contain

Pro Tips

• Never paste your JWT into a SERVER-side tool that sends data to a backend. Our parser is 100% client-side — the token stays in your browser
• Check the 'exp' (expiration) claim: JWTs typically expire 15-60 minutes after issuance. Short-lived tokens reduce the damage if a token is stolen
• The 'alg: none' attack: some JWT libraries historically accepted tokens with algorithm 'none' (no signature). Modern libraries reject this. If you see alg: none in a production token, it's a security concern
• JWT claims are readable by anyone who has the token — they're Base64-encoded, not encrypted. Never put sensitive data (passwords, credit cards, PII) in JWT claims

Frequently Asked Questions about Jwt Parser

Is it safe to decode my JWT online?

Decoding is safe because JWTs are Base64-encoded, not encrypted — anyone with the token can read the header and payload. However, our parser is fully client-side; your token never leaves your browser. Never paste tokens into server-side parsers.

How do I verify a JWT signature?

You need the secret key (for HMAC algorithms) or the public key (for RSA/ECDSA algorithms). Our parser doesn't verify signatures — use your application's JWT library or jwt.io's debugger for signature verification with your keys.

Free online Jwt Parser — no signup, 100% client-side processing. All data stays in your browser.