JWT Decoder
Decode and inspect JSON Web Tokens (JWT). View header, payload, and claims instantly in your browser.
Understanding JWTs
Header
Contains metadata about the token type and signing algorithm (e.g., HS256, RS256).
Payload
Contains claims - statements about the user and additional metadata like expiration time.
Signature
Cryptographic signature to verify the token has not been tampered with.
JWT Security Best Practices
- ✓Use short expiration times (exp claim) — set access tokens to expire within 15 minutes to minimize the window of compromise if a token is stolen.
- ✓Always validate the signature — never trust an unverified token. Verify the cryptographic signature on every request before processing claims.
- ✓Use RS256 (asymmetric) over HS256 (symmetric) for distributed systems where multiple services need to verify tokens without sharing a secret key.
- ✓Store tokens securely — use HttpOnly, Secure, SameSite cookies instead of localStorage to prevent XSS attacks from accessing tokens.
- ✓Implement token refresh — use long-lived refresh tokens (stored securely) to issue new short-lived access tokens without requiring re-authentication.
- ✓Include audience (aud) and issuer (iss) claims for validation to ensure tokens are only accepted by intended recipients from trusted issuers.
- ✗Never store sensitive data in the payload — JWTs are encoded, not encrypted. Anyone can decode and read the payload without the secret key.
- ✗Never accept the "alg": "none" header — always enforce a specific signing algorithm server-side to prevent signature bypass attacks.
Best Authentication & Identity Platforms (2026)
Secure your JWT-based authentication with battle-tested identity providers.
| Platform | Type | Free Tier | Price | Key Features | Link |
|---|---|---|---|---|---|
Auth0 Top Pick | Identity Platform | 7,500 MAU | $23/mo | Universal login, MFA, SSO, social connections | Visit |
Clerk Developer Auth | Developer Auth | 10,000 MAU | $25/mo | Prebuilt components, webhooks, session management | Visit |
Firebase Auth BaaS Auth | BaaS Auth | 50K MAU | Pay-as-you-go | Google sign-in, phone auth, anonymous auth | Visit |
AWS Cognito Cloud IAM | Cloud IAM | 50K MAU | $0.0055/MAU | User pools, identity pools, SAML/OIDC | Visit |
Okta Enterprise SSO | Enterprise SSO | Developer free tier | Custom pricing | Workforce identity, SCIM, adaptive MFA | Visit |
Our recommendation: Use Auth0 for the most comprehensive identity platform with enterprise-grade JWT handling, or Clerk for the best developer experience with prebuilt UI components. Both support RS256/ES256 signing, token rotation, and refresh token flows out of the box.
JWT Standard Claims Reference
These registered claims are defined in RFC 7519 and are widely used across JWT implementations.
| Claim | Full Name | Description | Example |
|---|---|---|---|
| iss | Issuer | Identifies the principal that issued the JWT | "https://auth.example.com" |
| sub | Subject | Identifies the principal that is the subject of the JWT | "user-1234" |
| aud | Audience | Identifies the recipients that the JWT is intended for | "https://api.example.com" |
| exp | Expiration Time | Time after which the JWT must not be accepted (Unix timestamp) | 1735689600 |
| nbf | Not Before | Time before which the JWT must not be accepted (Unix timestamp) | 1735603200 |
| iat | Issued At | Time at which the JWT was issued (Unix timestamp) | 1735603200 |
| jti | JWT ID | Unique identifier for the JWT to prevent token replay attacks | "a1b2c3d4-e5f6" |
All time-based claims (exp, nbf, iat) use Unix timestamps (seconds since January 1, 1970 UTC). Use our decoder above to automatically convert these to human-readable dates.
Frequently Asked Questions
What is a JSON Web Token (JWT)?
A JSON Web Token (JWT) is a compact, URL-safe token format defined in RFC 7519 for securely transmitting information between parties as a JSON object. It consists of three Base64URL-encoded parts separated by dots: a header (algorithm and type), a payload (claims about the user), and a signature (cryptographic verification). JWTs are widely used in modern authentication systems, especially in OAuth 2.0 and OpenID Connect flows.
Is it safe to decode JWTs in the browser?
Yes, decoding a JWT in the browser is safe because the payload is only Base64URL-encoded, not encrypted — meaning anyone with the token can already read it. This tool processes everything client-side with zero data sent to any server. However, you should never paste production tokens containing sensitive claims into untrusted online tools that may transmit data to external servers.
What is the difference between HS256 and RS256?
HS256 (HMAC with SHA-256) is a symmetric algorithm that uses the same secret key for both signing and verification. RS256 (RSA Signature with SHA-256) is an asymmetric algorithm that uses a private key for signing and a separate public key for verification. RS256 is preferred for distributed systems because services only need the public key to verify tokens, eliminating the need to share secret keys across services.
How do I handle expired JWTs?
When a JWT expires (the exp claim is in the past), your application should not accept it for authentication. The standard approach is to implement a refresh token flow: issue short-lived access tokens (15 minutes) alongside longer-lived refresh tokens (days or weeks). When the access token expires, the client sends the refresh token to obtain a new access token without requiring the user to log in again.
Should I store JWTs in localStorage or cookies?
HttpOnly, Secure, SameSite cookies are the recommended storage mechanism for JWTs because they are not accessible to JavaScript, protecting against XSS (cross-site scripting) attacks. Storing JWTs in localStorage makes them vulnerable to XSS — any script running on the page can read and exfiltrate the token. If you must use localStorage, ensure strict Content Security Policy (CSP) headers and input sanitization.
What are the security risks of JWTs?
Common JWT security risks include: algorithm confusion attacks (accepting "alg": "none" or switching between HS256/RS256), insufficient signature validation, storing sensitive data in unencrypted payloads, overly long expiration times, lack of token revocation mechanisms, and insecure storage in localStorage. Mitigate these by enforcing specific algorithms server-side, validating all claims, using short expiration times, and implementing token blacklists for logout.