Free Online JWT Decoder & Parser
Instantly decode, inspect, and validate JSON Web Tokens. View header, payload, claims, and expiration status — all securely in your browser.
Paste a JWT token above or click Sample to see it decoded in real-time.
All decoding happens in your browser — your token never leaves your device.
What is JWT?
A JSON Web Token (JWT) is an open standard (RFC 7519) that defines a compact and self-contained way for securely transmitting information between parties as a JSON object. This information can be verified and trusted because it is digitally signed.
The Three Parts of a JWT
- Header: Contains the token type ("JWT") and the signing algorithm (e.g., HS256, RS256). It is Base64Url-encoded to form the first part of the token.
- Payload: Contains the claims — statements about an entity and additional data. Claims include user information, permissions, and token metadata like expiration time.
- Signature: Created by signing the encoded header and payload with a secret or private key. It verifies that the token was not altered in transit.
Common Use Cases
- Authentication: JWTs are widely used for single sign-on (SSO) and session management. Once a user logs in, a JWT is returned and stored client-side, then sent with each subsequent request.
- Information Exchange: JWTs provide a compact way to securely transmit data between parties, ensuring the data has not been tampered with thanks to the digital signature.
How to Use
Decoding a JWT with our tool is quick and easy. Follow these steps:
- Paste your JWT token into the input box at the top of the page. You can also click the “Sample” button to load a test token.
- Click the “Decode” button — or simply let the tool decode automatically as you paste.
- View the decoded Header and Payload displayed in a clean, formatted JSON view below the input.
- Copy the results using the copy button, or download the decoded output as a JSON file for further analysis.
That's it — no sign-up, no installation, and no data leaves your browser.
FAQ
- Q: Is my JWT token safe?
- Yes, all decoding happens entirely in your browser. We never store, transmit, or log your tokens. Your data stays on your device.
- Q: What is a JWT used for?
- JWTs are commonly used for authentication and secure information exchange between a client and a server.
- Q: Can I decode expired tokens?
- Yes, you can decode any JWT regardless of its expiration status. The tool will show you the expiration claim so you can check it yourself.
- Q: What does “Invalid token” mean?
- It means the input does not match the expected JWT format (three Base64Url-encoded parts separated by dots). Check for typos, extra spaces, or missing characters.
- Q: Is this tool free?
- Yes, it is completely free with no usage limits, no sign-up required.
- Q: Can I use this on mobile?
- Yes, our tool is fully responsive and works on all devices including smartphones, tablets, and desktop computers.
- Q: Do you store my tokens?
- No, everything is processed locally in your browser. No token data is ever sent to or stored on any server.
- Q: What algorithms are supported?
- We support HS256, RS256, ES256, PS256, and other common JWT signing algorithms. The algorithm used is always displayed in the decoded header.
What Is a JWT?
A JSON Web Token (JWT) is a compact, URL-safe means of representing claims to be transferred between two parties. JWTs are commonly used for authentication and authorization in modern web applications and APIs. A JWT consists of three parts — a header, a payload, and a signature — encoded as a Base64Url string and separated by dots.
How to Use This JWT Decoder
Using our JWT decoder is simple and fast:
- Step 1 — Paste your token:Copy a JWT from your application or click the “Sample” button to load a test token.
- Step 2 — Instant decoding: The tool automatically decodes the header and payload in real-time as you type or paste.
- Step 3 — Inspect the results: View the formatted header, payload claims, signature, algorithm details, and expiration status.
- Step 4 — Copy or clear: Use the action buttons to copy the token or clear the input.
JWT Structure Explained
A JWT is composed of three Base64Url-encoded parts, separated by dots:
- Header:Contains metadata about the token type (typically “JWT”) and the signing algorithm used (e.g., HS256, RS256).
- Payload: Contains the claims — statements about an entity (usually the user) and additional data. Claims can be registered (like
iss,exp,sub), public, or private. - Signature:Created by signing the encoded header and payload with a secret or private key. The signature ensures the token hasn't been tampered with.
Common JWT Claims
JWTs include standard registered claims that provide important metadata:
- iss (Issuer): The principal that issued the token.
- sub (Subject): The subject of the token, often the user ID.
- aud (Audience): The intended recipient of the token.
- exp (Expiration Time): The time after which the token is no longer valid.
- iat (Issued At): The time the token was issued.
- nbf (Not Before): The time before which the token must not be accepted.
- jti (JWT ID): A unique identifier for the token.
Is This JWT Decoder Secure?
Yes. Our JWT decoder runs entirely in your browser. Your token is never sent to any server, stored, or shared. All decoding and parsing happens locally on your device, ensuring complete privacy and security. You can safely decode sensitive tokens without worrying about data leakage.
Frequently Asked Questions
What does a JWT decoder do?
A JWT decoder takes a Base64Url-encoded JWT string and decodes it into its three components: the header, the payload (containing claims), and the signature. It formats the JSON for easy reading and displays additional information like expiration status and algorithm details.
Can this tool validate JWT signatures?
This tool decodes and inspects JWTs but does not perform cryptographic signature verification. Signature verification requires the secret or public key, which should be done server-side in your application.
Is decoding a JWT safe?
Yes. Decoding a JWT simply reads the Base64Url-encoded content. The payload and header are not encrypted — they are only encoded. However, the signature ensures integrity, so never trust a token's claims without verifying its signature on your server.
Can I use this tool on my phone?
Yes! Our JWT decoder is fully responsive and works on all devices including phones, tablets, and desktop computers.
Want to learn more about JWT?
Check out our blog for in-depth guides on JWT structure, security best practices, and authentication strategies.
Read Our Blog