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Browser-based JWT utility

JWT Decoder — Free Online Tool

Decode JSON Web Tokens instantly in your browser. Inspect headers, payloads, and signatures without sending any data to a server.

JWT Token

What Is a JSON Web Token (JWT)?

JSON Web Token (JWT) is an open standard for securely transmitting information between parties as a JSON object. This information can be verified and trusted because it is digitally signed. JWTs can be signed using a secret (with the HMAC algorithm) or a public/private key pair using RSA or ECDSA.

Although JWTs can be encrypted to also provide secrecy between parties, this tool focuses on signed tokens. Signed tokens can verify the integrity of the claims contained within them, while encrypted tokens hide those claims from other parties.

JWT Structure

A JWT consists of three parts separated by dots, which are Header, Payload, and Signature.

  1. Header — Typically consists of two parts: the type of token (JWT) and the signing algorithm being used, such as HMAC SHA256 or RSA.
  2. Payload — Contains the claims. Claims are statements about an entity (typically the user) and additional metadata. There are three types of claims: registered, public, and private.
  3. Signature — To create the signature part you have to take the encoded header, the encoded payload, a secret, the algorithm specified in the header, and sign that.

When Should You Use JWTs?

Here are some scenarios where JSON Web Tokens are useful:

  • Authentication — This is the most common scenario for using JWT. Once the user is logged in, each subsequent request will include the JWT, allowing the user to access routes, services, and resources that are permitted with that token.
  • Information Exchange — JSON Web Tokens are a good way of securely transmitting information between parties. Because JWTs can be signed, you can be sure the senders are who they say they are.

How to Use This JWT Decoder

  1. 1. Paste your JWT in the input field above.
  2. 2. Inspect the decoded data — The tool will automatically decode and display the header, payload, and signature.
  3. 3. Copy or download the decoded JSON for further inspection.

FAQ

Is JWT secure?

JWT itself is just a format. Its security depends on how you use it. Always use HTTPS to prevent tokens from being stolen in transit, use short expiration times, and never store sensitive data in the payload.

Can anyone decode my JWT?

Yes. The header and payload are only base64url encoded, not encrypted. Anyone can decode them. The signature ensures that the token hasn't been tampered with, but it doesn't hide the content.

Does this tool validate the signature?

This tool only decodes the JWT for inspection. It does not validate the signature, as that would require access to the secret or public key used to sign the token.