This tool runs 100% inside your browser engine.
Your tokens, headers, and payloads are processed exclusively by your local JavaScript runtime and never leave your device. No network requests are made. No analytics, logs, or telemetry capture your data. You can verify this by opening DevTools → Network tab while using the tool.
JWT Decoder & Inspector
Decode, analyze, and audit JSON Web Tokens — 100% client-side, zero network transmission
{
"alg": "HS256",
"typ": "JWT"
}eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9
{
"sub": "usr123456",
"name": "Alice Mali",
"iat": 1719296000,
"exp": 1719382400,
"iss": "https://auth.primebytelabs.com",
"aud": "api.primebytelabs.com",
"role": "admin"
}eyJzdWIiOiJ1c3IxMjM0NTYiLCJuYW1lIjoiQWxpY2UgTWFsaSIsImlhdCI6MTcxOTI5NjAwMCwiZXhwIjoxNzE5MzgyNDAwLCJpc3MiOiJodHRwczovL2F1dGgucHJpbWVieXRlbGFicy5jb20iLCJhdWQiOiJhcGkucHJpbWVieXRlbGFicy5jb20iLCJyb2xlIjoiYWRtaW4ifQ
SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c
Signature verification requires the secret key (HMAC) or public key (RSA/ECDSA) and cannot be performed client-side without it. Use your auth server to validate authenticity.
HMAC-SHA2
Symmetric — same secret signs and verifies. Never expose secret client-side.
6/25/2024, 6:13:20 AM
Tue, 25 Jun 2024 06:13:20 GMT
747 days ago6/26/2024, 6:13:20 AM
Wed, 26 Jun 2024 06:13:20 GMT
Expired 746 days agousr123456
The principal entity the token is about (user ID, etc.)
Alice Mali
Display name of the authenticated user
6/25/2024, 6:13:20 AM
Unix timestamp when the token was issued
6/26/2024, 6:13:20 AM
Unix timestamp after which the token is invalid
https://auth.primebytelabs.com
The entity that issued the JWT (auth server URL)
api.primebytelabs.com
Recipients this JWT is intended for
admin
User role/permission scope
We design production-grade JWT auth flows & API gateway policies.
Step-by-Step Guide
Paste Your JWT Token
Copy your JSON Web Token from your auth header, application logs, or debug session and paste it into the input field. A live sample is pre-loaded so you can explore immediately.
Inspect Decoded Structure
The token is instantly split into its three Base64URL parts — Header, Payload, and Signature — each decoded and displayed as formatted JSON with raw encoding shown below.
Audit Algorithm & Claims
The algorithm analysis panel identifies the signing family (HMAC, RSA, ECDSA), its security rating, and contextual guidance. Each claim is mapped to its RFC 7519 standard description.
Review Security Flags
The security audit panel automatically scans for critical issues: missing expiry, expired tokens, the dangerous 'none' algorithm, and HMAC tokens without time bounds.
Frequently Asked Questions
Is it safe to paste my JWT into an online decoder?
Only if the tool is 100% client-side. Our decoder runs entirely in your browser using JavaScript — no token, payload, or claim data is transmitted to any server. You can verify this by disabling your network connection and the tool will still work perfectly.
What is the difference between JWT header, payload, and signature?
A JWT has three Base64URL-encoded sections separated by dots. The Header contains metadata like the algorithm (alg) and token type (typ). The Payload contains the claims — data about the user or session. The Signature is a cryptographic hash of the header and payload, used to verify the token hasn't been tampered with.
Which JWT algorithm (alg) should I use in production?
Use RS256 or ES256 for production. These asymmetric algorithms separate signing (private key) from verification (public key), making them safe for public APIs. Avoid HS256 unless you fully control both the issuer and consumer. Never use 'alg: none' — it disables signature verification entirely.
Why can't this tool verify the JWT signature?
Signature verification for HMAC (HS256/384/512) requires the secret key, and for RSA/ECDSA (RS256, ES256, etc.) requires the public key. Exposing these client-side would be a critical security vulnerability. Use your auth server or a backend verification endpoint to validate signatures.