🔑 Décodeur JWT — Analyser les JSON Web Tokens

Decode any JWT token and inspect the header, payload, and expiration. Check if a token is expired. 100% client-side — your token never leaves your browser.

Paste your JWT (the eyJ... string) and click Decode. The tool splits it into header, payload, and signature, decodes each Base64URL part, and shows the JSON. If the payload has an exp field, the tool shows whether the token is still valid or has expired.

JWT Token

How to Use

Paste your JWT

Copy your JWT token (starting with eyJ) and paste it into the input field.

Click Decode

Press Decode to instantly split and decode all three parts: header, payload, and signature.

Inspect the token

Read the decoded JSON, check expiration dates, algorithm, and any custom claims in the payload.

Frequently Asked Questions

What is a JWT? +

A JSON Web Token (JWT) is a compact, URL-safe token used for authentication and information exchange. It consists of three Base64URL-encoded parts separated by dots: Header.Payload.Signature.

Is it safe to paste my JWT here? +

Yes. This tool runs 100% in your browser — your token is never sent to any server. However, never share JWTs containing sensitive data in public forums or untrusted tools.

Can this tool verify the JWT signature? +

No. Signature verification requires the secret key or public key used to sign the token, which only your server knows. This tool decodes and displays the token contents only.

What does "exp" mean in the payload? +

"exp" is the expiration time as a Unix timestamp (seconds since Jan 1, 1970). This tool automatically converts it to a human-readable date and shows whether the token has expired.

What is the difference between "iat" and "nbf"? +

"iat" (issued at) is when the token was created. "nbf" (not before) is the earliest time the token is valid. Both are Unix timestamps.

Guide : Décodeur JWT

Qu'est-ce que c'est ?

Le Décodeur JWT décompose les JSON Web Tokens en leurs trois parties : en-tête, charge utile et signature — et affiche les claims de manière lisible.

Il est indispensable pour déboguer les problèmes d'authentification, vérifier l'expiration des tokens et inspecter les permissions encodées.

Comment utiliser

Collez votre JWT (format xxxxx.yyyyy.zzzzz) dans le champ d'entrée.
L'en-tête et la charge utile sont décodés et affichés en JSON formaté.
Vérifiez les claims comme exp, iat, sub et iss.
Notez que la vérification de signature nécessite la clé secrète.

Conseils professionnels

Vérifiez toujours exp côté serveur — un JWT décodable n'est pas forcément valide.
Ne mettez jamais de données sensibles dans la charge utile JWT — elle n'est qu'encodée, pas chiffrée.