X.509 / CSR / Private Key Decoder
Paste a PEM: subject, validity, SANs, fingerprints. Parsing happens locally in a Web Worker, no upload.
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What is Certificate Decoder?
PEM decoder that parses X.509 certificates, CSRs and private keys, surfacing subject, issuer, validity, SANs, key usage, signature and fingerprints (MD5, SHA-1, SHA-256).
How to use this tool?
Paste your PEM, the tool auto-detects the type and shows decoded fields with a colored expiration badge (green/orange/red).
Benefits
- Auto type detection
- MD5 / SHA-1 / SHA-256 fingerprints
- Colored expiration badge
- SANs and key usage
- Web Worker (sandboxed parsing)
- 100% browser
Frequently Asked Questions
- Which formats are supported?
- X.509 certificates (BEGIN CERTIFICATE), certificate signing requests (BEGIN CERTIFICATE REQUEST) and PEM private keys (RSA, EC, PKCS#8). The type is auto-detected.
- Is my certificate sent to a server?
- No. Parsing runs in a Web Worker using node-forge. No data ever leaves your browser.
- What happens if I paste a private key?
- The tool only displays the algorithm type and key size. Raw cryptographic material is never displayed or stored.
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Use →What is Certificate Decoder?
PEM decoder that parses X.509 certificates, CSRs and private keys, surfacing subject, issuer, validity, SANs, key usage, signature and fingerprints (MD5, SHA-1, SHA-256).
How to use this tool?
Paste your PEM, the tool auto-detects the type and shows decoded fields with a colored expiration badge (green/orange/red).
Benefits
- Auto type detection
- MD5 / SHA-1 / SHA-256 fingerprints
- Colored expiration badge
- SANs and key usage
- Web Worker (sandboxed parsing)
- 100% browser
Frequently Asked Questions
- Which formats are supported?
- X.509 certificates (BEGIN CERTIFICATE), certificate signing requests (BEGIN CERTIFICATE REQUEST) and PEM private keys (RSA, EC, PKCS#8). The type is auto-detected.
- Is my certificate sent to a server?
- No. Parsing runs in a Web Worker using node-forge. No data ever leaves your browser.
- What happens if I paste a private key?
- The tool only displays the algorithm type and key size. Raw cryptographic material is never displayed or stored.
Similar Tools
SSH Key Generator
Generate SSH keys (RSA, Ed25519, ECDSA) directly in your browser. OpenSSH format, optional passphrase. 100% local, never sent.
Use →File Hash Checker
Calculate and compare MD5, SHA-1, SHA-256, or SHA-512 file fingerprints. 100% in the browser. Verify your downloads.
Use →HTTP Headers Decoder
Paste HTTP response headers: CSP, Cache-Control, HSTS, Set-Cookie, Authorization — explained directive by directive. No outbound calls.
Use →Encrypted Secret Sharing
Share a password or API key via an encrypted, single-use link (burn after reading). AES-256, free.
Use →