Decode JWT header and payload with weak-algorithm and expiry warnings — signature is not verified.
- Free
- No signup
- Fast
- Privacy-friendly
Free · API · MCPToolYour platform
Use JWT Decoder three ways
The free JWT Decoder on this page works in your browser. The same workflow is available via REST API for apps and via MCP for Cursor, Claude, and other agents — one API key, one plan, one quota. This tool is part of the security-apis module under Security Tools.
- Free in browserUse JWT Decoder here — no account required.
- REST APICall from your server with
X-Api-Key. - MCP for agentsConnect Cursor or Claude to ToolYour MCP with the same key.
- 1. Get an API keySign in and open Dashboard → API Keys (works for REST and MCP).
- 2. Call or connectUse the REST API from your server, or paste the MCP URL into your agent config.
- 3. Same qualityOutput matches the free web tool across all three surfaces.
What is JWT Decoder?
Debugging auth often starts with reading a JWT header and payload without verifying the signature in the browser. ToolYour JWT Decoder base64url-decodes header and payload, flags alg=none / HMAC caveats, and warns on exp/nbf. Signature is not verified — never treat decode-only output as proof of authenticity. REST/MCP POST /api/v1/security-apis/jwt-decoder with { "token": "..." }.
What are common questions about JWT Decoder?
Do you verify the signature?
No. This is decode-only. Verify HMAC/RSA signatures in your own backend with the correct key.
Is it safe to paste production JWTs?
Prefer redacted or staging tokens. A JWT can embed PII in claims; treat pastes like secrets.
What are the key features of JWT Decoder?
Header and payload JSON
Pretty-printed claims for quick debugging.
Safety warnings
Flags none/HMAC algorithms and expired or not-yet-valid tokens.
How do you use JWT Decoder?
Paste the JWT
header.payload.signature format (signature optional for decode).
Read warnings first
Fix alg and lifetime issues before trusting claims in your app.
Agent usage
hasApi tools are callable from MCP with one key — useful when agents need to inspect token shape during auth troubleshooting.
Where do you browse more security tools tools?
- Security Tools tools
Browse the full Security Tools category on ToolYour.
- AI Tools tools
PII scrub, resume match, transcription, video summarize, and YouTube analysis. Free in the browser; API-backed
- File Converter tools
Convert PDF↔Word, compress images, and change formats online. Free in browser · REST · MCP. No signup for typi
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