JWT · Security

JWT Decoder Online: Read Any JWT Token in Seconds

Learn how to decode JWT tokens instantly — what the parts mean, how to use our free tool, and what to check for security.

5 min read → Open JWT Decoder Tool

What is a JWT Token?

A JWT (JSON Web Token) is a compact, URL-safe token used for authentication and information exchange. You'll see them in Authorization: Bearer ... headers, cookies, and URL parameters.

Every JWT has three parts separated by dots (.):

header.payload.signature

Header — algorithm and token type
Payload — the actual claims (user ID, expiry, roles)
Signature — cryptographic proof the token hasn't been tampered with

How to Decode a JWT Token

The header and payload are just Base64URL-encoded JSON — you can decode them without the secret key. The signature verification requires the secret.

Using our online JWT decoder:

Paste your JWT token into the input field
The tool instantly splits and decodes the header and payload
Check the exp claim to see when it expires
Check iat for when it was issued, sub for the subject

Common JWT Claims

Claim	Meaning
`sub`	Subject (usually user ID)
`iat`	Issued at (Unix timestamp)
`exp`	Expiration time (Unix timestamp)
`iss`	Issuer
`aud`	Audience
`nbf`	Not before (token valid after this time)

Is It Safe to Decode JWTs Online?

Our JWT decoder runs entirely in your browser using JavaScript. No data is sent to any server. The token never leaves your device.

That said: never decode JWTs that contain sensitive production secrets in a tool you don't trust. For sensitive work, use our tool (client-side only) or decode locally with:

echo "eyJhbGciOi..." | cut -d. -f2 | base64 -d 2>/dev/null | python3 -m json.tool

JWT Debugging Tips

Token expired? Check exp — it's a Unix timestamp. Convert to human-readable with our Timestamp Converter.
Algorithm mismatch? Check the alg field in the header. RS256 uses RSA keys, HS256 uses a shared secret.
Missing claims? Your backend may expect specific claims that aren't present.

Try the Tool

→ Open the free JWT Decoder — no signup, no limits, works offline.