Why We Built This
JSON Web Tokens are everywhere — in login flows, API gateways, microservice communication, and single sign-on systems. Developers routinely need to peek inside a token to check an expiration time, confirm a claim value, or debug a failing auth flow. Existing tools either require an account, send your token to a server for processing, or bury the decoder under layers of unrelated features.
jwtdecode.io was created to solve that problem: give developers a fast, clean tool that decodes and verifies JWTs entirely in the browser, with zero server-side processing. No sign-up, no tracking pixels, no data collection. Paste a token, see the result.
How It Works
When you paste a JWT into the decoder, all processing happens locally through JavaScript running in your browser. The token is split into its three Base64URL-encoded parts — header, payload, and signature — and each part is decoded and displayed as readable JSON.
Signature verification is powered by the Web Crypto API, a browser-native cryptographic library. This means your secret keys and tokens never leave your machine — not even temporarily. We support all nine standard signing algorithms: HS256, HS384, HS512, RS256, RS384, RS512, ES256, ES384, and ES512.
Privacy by Design
No Server Processing
Tokens and keys are processed entirely in your browser. Nothing is transmitted over the network.
No Account Required
Use the tool instantly — no registration, no email collection, no login walls.
No Token Storage
We don't store, log, or persist any tokens. When you close the tab, your data is gone.
Minimal Analytics
We use anonymous page-view analytics to understand traffic patterns. No personal data is collected.
For full details, read our privacy policy.
Features
- Instant decoding — Paste a token and see the header and payload immediately, with syntax-highlighted JSON output
- Signature verification — Verify HMAC, RSA, and ECDSA signatures using the Web Crypto API
- Multiple key formats — Supports PEM-encoded keys and JWK (JSON Web Key) format for asymmetric algorithms
- Copy to clipboard — One-click copy for the decoded payload, useful for scripting and debugging
- Works offline — Once loaded, the tool functions without an internet connection
- Mobile-friendly — Responsive layout that works on phones and tablets
Educational Resources
Beyond the decoder itself, we maintain a library of guides to help developers understand and implement JWTs correctly:
Complete JWT Guide
Token structure, claims, signatures, and how everything fits together
Algorithm Reference
HS256 vs RS256 vs ES256 — when to use each signing algorithm
JWT Claims Reference
Registered, public, and private claims explained with examples
Security Best Practices
Common vulnerabilities and how to avoid them in production
JWT Authentication Patterns
Access tokens, refresh tokens, and real-world auth flows
JWT vs Sessions
Stateless tokens vs server-side sessions — trade-offs and guidance
Technology
jwtdecode.io is built with Next.js and deployed as a static site on Cloudflare Pages, providing fast load times globally. The cryptographic operations use the Web Crypto API, which is built into all modern browsers and provides hardware-accelerated cryptographic primitives.