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X.509 certificate and CSR inspector

Paste a PEM certificate or PKCS#10 CSR — subject, issuer, validity window, SANs, key facts, and extensions, parsed by pkijs in your tab. Nothing fetched, nothing uploaded.
PEM certificate or CSRInspect

- No chain validation — that needs trusted root stores and revocation data (OCSP/CRL) this offline page refuses to contact.
- “Valid now” means the validity window contains your clock — never that anyone trusts the certificate.
- No private key handling: paste a certificate or CSR, and a CSR’s whole point is that the private key never left your machine.
Nothing in yet

Paste, drop, or type to begin. Everything stays on this device.

paste a certificate or CSR PEM

Next door in Web

- SAML inspector (/web/saml)
- JWK / JWKS (/web/jwk)
All web tools (/web)

Canonical HTML: https://nutter.tools/web/certificate
Markdown version: https://nutter.tools/web/certificate/index.md
Plain-text version: https://nutter.tools/web/certificate/index.txt
Agent index: https://nutter.tools/llms.txt