Verify HS*/RS*/ES* JWT signatures with a pasted secret, PEM public key, or JWK — complements decode-only JWT Decoder.
- Free
- No signup
- Fast
- Privacy-friendly
Free · API · MCPToolYour platform
Use JWT Signature Verifier three ways
The free JWT Signature Verifier 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 Signature Verifier 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 Signature Verifier?
Decode alone is not auth. JWT Signature Verifier checks HS* with a secret or RS*/ES* with a public key/JWK. Use <a href="/security-tools/jwt-decoder">JWT Decoder</a> for claims-only inspection and <a href="/security-tools/secret-leak-scanner">Secret Leak Scanner</a> if tokens appeared in logs. REST/MCP: /api/v1/security-apis/jwt-signature-verifier.
What are common questions about JWT Signature Verifier?
What does JWT Signature Verifier do?
Verify HS*/RS*/ES* JWT signatures with a pasted secret, PEM public key, or JWK — complements decode-only JWT Decoder.
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 Signature Verifier?
Free browser access
Use JWT Signature Verifier without subscription or registration.
Cross-device support
Runs on desktop, tablet, and mobile browsers.
Privacy-focused
Inputs are processed to produce output and not kept longer than needed.
How do you use JWT Signature Verifier?
Open the tool
JWT Signature Verifier loads instantly — no signup required.
Provide input
Paste, type, or upload the input the tool expects.
Copy or download
Use the result in your workflow — outputs are yours to keep.
Auth helpers cluster
Which secrets & auth tools sit in this cluster?
Where do you browse more security tools tools?
- Security Tools tools
Browse the full Security Tools category on ToolYour.
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