JWT Decoder

JWTs (JSON Web Tokens) are used everywhere for authentication. When you log into an app, the server may return a JWT that your client sends with each request. A JWT has three parts—header, payload, and signature—each Base64-encoded and separated by dots. The payload usually contains user ID, email, expiration, and other claims. Decoding a JWT without verifying the signature lets you inspect its contents. This tool does exactly that: paste a JWT and see the decoded header and payload. No verification, no server round-trip—just inspection.

Developers use it when debugging auth flows. "What's in this token? When does it expire? What claims are present?"—paste the token and see. The header shows the algorithm (e.g. HS256, RS256). The payload shows claims like sub (subject), exp (expiration), iat (issued at). Expiration is usually a Unix timestamp; use a timestamp converter to see the date. Understanding token contents helps when fixing login bugs, troubleshooting API access, or implementing token refresh.

Important: this tool does not verify the signature. It trusts that the token is valid Base64 and shows what's inside. A forged or tampered JWT would still decode; the payload could be lies. Use this for debugging and inspection only. Never use decoded token data for security decisions without verification. In production, your backend must verify the signature with the correct key. This tool is a peek under the hood, not a security validator.

Tokens are often long. Copy them from browser storage, network tabs, or logs. Paste here and decode. All processing is client-side; your token never leaves your device. If you're handling sensitive tokens, that matters. Use it to understand how your auth system works, debug expiry issues, or learn JWT structure. Fast, simple, and private.