CSR Decoder

A Certificate Signing Request (CSR) is a block of encoded text sent to a Certificate Authority (CA) when applying for an SSL/TLS certificate. It contains important information about the organization and the public key that will be used in the certificate. Inspecting a CSR before submission helps catch errors that could delay or prevent certificate issuance.

This decoder parses a CSR in PEM format and extracts all relevant details: subject fields (Common Name, Organization, Organizational Unit, Locality, State, Country), public key algorithm (RSA or EC) and key size, signature algorithm, and X.509 extensions including Subject Alternative Names (SANs) and key usage attributes.

Common use cases include verifying CSR content for accuracy before submitting to a CA, checking the key algorithm and strength for security compliance, reviewing SAN entries for multi-domain certificates, auditing certificate requests in security workflows, and troubleshooting CSR-related errors.

1. Get your CSR — Obtain your CSR file in PEM format. It should start with -----BEGIN CERTIFICATE REQUEST----- and end with -----END CERTIFICATE REQUEST-----.
2. Paste the CSR — Copy and paste the full PEM content into the input textarea.
3. Click Decode — The tool parses the CSR and displays the decoded information in organized cards.
4. Review subject fields — Check the Subject card for Common Name (CN), Organization (O), and other identifying information.
5. Inspect key and extensions — Verify the public key algorithm and size, signature algorithm, and any SAN entries or key usage extensions.
6. Try examples — Use the sample buttons (RSA 2048, EC P-256, With SAN) to load test data and explore the tool.