What is a JSON Web Token (JWT)?

A JWT is a compact, URL-safe token used to securely transmit information between parties as a JSON object. It consists of three parts a header, a payload, and a signature each Base64URL encoded and separated by dots.

Is it safe to decode a JWT in this tool?

Yes. The decoder processes everything entirely in your browser no token data is sent to any server. However, you should never share JWTs containing sensitive production credentials or user data in any public tool.

What's the difference between decoding and verifying a JWT?

Decoding simply reads the contents of a JWT by Base64URL decoding its parts anyone can do this without a secret key. Verification, on the other hand, checks whether the token's signature is valid using the correct secret or public key, confirming the token hasn't been tampered with.

JWT Decoder & Encoder

About JWT Decoder & Encoder

JWT encoder and decoder lets you both inspect existing tokens and build new ones directly in the browser. Paste a token to decode its claims, or fill in a header and payload to generate a signed JWT for testing. This free, no-signup tool is useful for developers building authentication systems, debugging API access issues, or verifying token structure during integration work.

JWT Decoder and Encoder is a free browser-based tool for inspecting and creating JSON Web Tokens (JWTs). JWTs are a standard format for transmitting authentication and authorization information between services, typically used in REST API authentication flows where a server issues a signed token after login and the client sends it with each subsequent request. This tool accepts any JWT and decodes its header, payload, and signature components, displaying them as formatted JSON. Users can also construct new tokens by entering a payload and a secret key. The tool runs entirely in the browser, which is important for security: pasting a production JWT into a third-party server-based tool would expose sensitive credentials. No account or installation is required.

JWT Decoder and Encoder is used primarily for development and debugging tasks in API-driven applications. When implementing JWT authentication in a backend service, inspecting the decoded payload confirms that the token contains the expected claims: user ID, roles, issued-at time, expiration time, and any custom fields. This is faster than adding debug log statements to the application code and then running the authentication flow. When a JWT is rejected by an API, decoding it reveals whether the issue is an expired token (the exp claim is in the past), a missing required claim, or an unexpected issuer value. The header component shows the algorithm used for signing, which is important for matching the verification logic in the backend. Common algorithms are HS256 (HMAC with SHA-256, using a shared secret) and RS256 (RSA with SHA-256, using a public/private key pair). The tool supports construction of new tokens with a custom payload and a shared secret, which is useful for generating test tokens during development without running the full authentication flow. Because JWTs can contain sensitive information such as user identifiers, roles, and session data, using a browser-based tool that processes everything locally is significantly safer than pasting tokens into a server-based decoder. The tool does not persist any entered values and clears state on page reload.

How to use JWT Decoder & Encoder

Paste your JWT token or JSON
Choose to decode or encode
View results or copy the output

Frequently Asked Questions

What is a JSON Web Token (JWT)?: A JWT is a compact, URL-safe token used to securely transmit information between parties as a JSON object. It consists of three parts a header, a payload, and a signature each Base64URL encoded and separated by dots.
Is it safe to decode a JWT in this tool?: Yes. The decoder processes everything entirely in your browser no token data is sent to any server. However, you should never share JWTs containing sensitive production credentials or user data in any public tool.
What's the difference between decoding and verifying a JWT?: Decoding simply reads the contents of a JWT by Base64URL decoding its parts anyone can do this without a secret key. Verification, on the other hand, checks whether the token's signature is valid using the correct secret or public key, confirming the token hasn't been tampered with.