Decode JWT header and payload with weak-alg warnings — signature is not verified here.
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JWT Decoder
Decode ≠ verify. This only reads header/payload claims. To check the signature, use JWT Signature Verifier.
Waiting for bot check… this usually takes a second.
What next?
Keep going with JWT Decoder
Finish this check in the browser, then pick the path that matches how you work — another related tool, REST for apps, or MCP for agents.
- 1. Related check
After this result, run Secret leak scanner for the next signal.
Secret leak scanner - 2. Automate with API
Same job from your server with
Create free accountX-Api-Key. Free tier includes 500 credits/month. - 3. Hand off to an agent
Connect Cursor or Claude to ToolYour MCP — plan → run → verify.
MCP setup
What is JWT Decoder?
Decode-only JWT inspection with weak-alg warnings — signature is not verified here. Use JWT Signature Verifier to verify signatures. If tokens leaked into logs, run Secret Leak Scanner. Agents use auth-token-hygiene playbooks and verify after rotations — see <a href="/developers/security-audit">security audit</a>.
What are common questions about JWT Decoder?
What does JWT Decoder do?
Decode JWT header and payload with weak-alg warnings — signature is not verified here.
Is this available via API and MCP?
Yes. Same route under /api/v1/security-apis/{slug} with one ToolYour API key.
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.
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 the remote MCP server 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.
- 1Create a free accountGet an API key for REST and MCP — 500 credits/month on the free tier.
- 2Connect or callPaste the MCP URL into Cursor/Claude, or call REST with
X-Api-Key. - 3Same key & creditsBrowser smoke-checks stay free; API-backed runs share one monthly credit quota.
- Free in browserUse JWT Decoder here — no account required.
- REST APICall from your server with
X-Api-Key. - Remote MCP serverSame job from Cursor or Claude via the ToolYour remote MCP server — one API key with REST.
Which secrets & auth tools sit in this cluster?
- Secret leak scanner
Heuristic API key and token leaks in pasted text.
- JWT signature verifier
Verify HMAC or asymmetric JWT signatures.
- Webhook signature verifier
GitHub, Stripe, or raw HMAC webhook checks.
- HMAC generator
Generate or verify HMAC digests.
- Bcrypt / Argon2 hash
Password KDF hashes for storage tests.
Where does this job fit on ToolYour?
Where do you browse more security tools tools?
- Security Tools tools
Browse the full Security Tools category on ToolYour.
- Developer Tools tools
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Which toolkits include JWT Decoder?
- Security Toolkit
HTTP security headers, TLS, cookies, CORS, redirects, DNS, secrets, JWT, passwords, hashes, HMAC, bcrypt, security.txt, SRI, and email auth — plus agent playbooks for full audits and ship gates.
- Developer Toolkit
JSON/XML/SQL formatters, encoders, UUID/timestamp/regex, JSON codegen, JWT minting, HTTP headers, request builders, cron, minifiers, and color conversion — plus security and text peers.