JWT Encoder and Decoder
Free online JWT Encoder and Decoder that runs directly in your browser.
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1Enter data
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2Click the button
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3Get the result
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JWT Encoder and Decoderis an online tool for developers to decode, parse, and verify JWT (JSON Web Token) tokens. Paste a token to instantly see its header, payload and signature - without writing any code.
What is JWT?
JWT (JSON Web Token) is an open standard (RFC 7519) for defining a secure, compact way to pass information between pages as a JSON object. JWTs are commonly used in authentication and authorization systems - especially RESTful API architectures and Single Page Applications (SPAs).
The JWT token consists of three parts separated by dots:header.payload.signature. Each part is Base64Url encoded.Headercontains token type (JWT) and encryption algorithm (HS256, RS256, ES256).Payloadcontains claims - claims about the user (sub, email, role) and token (iat - issued at, exp - expiration).Signatureis a signature verifying the authenticity of the token.
How to use JWT decoder?
Paste the JWT token into the text box. The tool automatically decodes the Base64Url of each section and displays: header content (algorithm, type) in readable JSON, payload content (user and token claims) with automatic date parsing (iat, exp, nbf from timestamp to readable date), token expiration warning (if exp is in the past) and signature structure. Signature verification requires a secret key (HS256) or public key (RS256) - without them we can only decode, not verify.
JWT security - what is worth knowing?
JWTs are signed, not encrypted (unless you use JWE). This means that the payload is only Base64Url encoded - anyone who has the token can decode it and read the claims. Never enter confidential data (passwords, credit card details) in JWT. Always set a short expiration time (exp) - access tokens typically 15 minutes to 1 hour, refresh tokens - a few days. Use HTTPS - A token sent over an unencrypted connection may be intercepted.
Common JWT claims
sub(subject) - user ID.iat(issued at) - token issue time (Unix timestamp).exp(expiration) - token validity time.nbf(not before) - token valid only from this moment.iss(issuer) - token issuer.aud(audience) - intended for whom.jti(JWT ID) - A unique token identifier.
FAQ
Is JWT decoding by this tool safe?
The tool works on the client side (in the browser) - the token is not sent to the server. Base64 decoding is done locally in JavaScript. However, for production tokens containing sensitive data, always prefer local development tools (e.g. offline jwt.io or CLI tools).
What is the difference between HS256 and RS256 in JWT?
HS256 (HMAC SHA-256) uses a single secret key for signing and verification - simpler, but the key must be known to both the issuer and the verifier. RS256 (RSA SHA-256) uses a key pair: private for signing and public for verification - more secure in distributed systems where different services verify tokens.
How to check if a JWT has expired?
Check the value of claimexp- this is the Unix timestamp (seconds since 1970-01-01). Ifexpis in the past (less than the current timestamp), the token has expired. Our decoder automatically converts the timestamp to a readable date and displays a warning if the token has expired.
Is it possible to change the JWT token payload?
Technically yes - you can decode, modify and re-encode Base64. However, without knowing the secret key (HS256) or private key (RS256), the correct signature cannot be generated. The token validation server will reject a token with an invalid signature.
Where to store the JWT in a web application?
The most popular options are: localStorage/sessionStorage (convenient, but vulnerable to XSS attacks), HttpOnly cookies (more secure - not available for JavaScript, protected against XSS), memory (JS variable - most secure, but the token disappears after refreshing the page). For production applications, HttpOnly cookies with the Secure and SameSite=Strict attributes are recommended.