Need to inspect a JSON Web Token (JWT) quickly and securely? Use our free Online JWT Decoder tool below. Simply paste your encoded token into the input field to parse and view its Header, Payload, and Signature in real-time.
What is a JSON Web Token (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. Because this information is digitally signed, it can be verified and trusted.
JWTs are most commonly used for Stateless Authentication and Information Exchange across web applications and microservices.
The Structure of a JWT
A standard JSON Web Token consists of three distinct parts separated by dots (.):
- Header: Contains the metadata for the token, typically specifying the token type (JWT) and the signing algorithm used (such as HS256 or RS256).
- Payload: Contains the "claims" or the actual data being passed (such as user ID, username, roles, and token expiration time
exp). - Signature: Created by taking the encoded header, encoded payload, a secret key, and signing it with the algorithm specified in the header to ensure the token wasn't tampered with.
Why Use This Client-Side JWT Decoder?
🔒 100% Secure & Private: Security is paramount when handling authentication tokens. Unlike other web-based utilities that send your data to a backend server, this JWT decoder operates entirely in your browser. Your token never leaves your machine, ensuring your sensitive session variables and keys remain private.
- Real-Time Parsing: No need to hit a "Submit" button. As you type or paste your token, the tool automatically splits, formats, and syntax-highlights your JSON data.
- Color-Coded Visuals: The tool matches the standard JWT coloring scheme (Header in teal/green, Payload in orange/brown, and Signature in purple) so you can visually map the encoded string directly to its decoded output.
- Developer Friendly: Built using clean, modern styling optimized for mobile, desktop, and dark mode environments.
Frequently Asked Questions (FAQ)
1. Is it safe to decode my JWT online?
Yes, it is entirely safe if the tool is client-side. Our tool processes the entire decoding execution locally inside your browser via vanilla JavaScript. No data is transmitted to an external server or saved in a database. However, you should still practice caution and avoid putting tokens from production environments with highly critical secrets into unverified websites.
2. Can I use this tool to modify a JWT?
This specific tool is designed as a read-only inspector and viewer. Modifying a token would invalidate its cryptographic signature. If your application attempts to process a manually altered token without a matching signature recalculation, it will reject it as an unauthenticated request.
3. What does "Invalid base64url encoding" mean?
If our decoder displays an error, your string might be missing pieces, include trailing spaces, or lack standard JWT formatting. Ensure that your token contains exactly two periods (.) separating the three required sections.
4. What are common JWT claims?
sub(Subject): The unique identifier for the user or entity.iat(Issued At): The exact Unix timestamp when the token was created.exp(Expiration Time): The timestamp determining when the token becomes invalid.iss(Issuer): The authority or server that generated the token.