Paste PEM CSR; see all fields decoded. Free CSR decoder online.
The CSR Decoder takes a PEM-encoded Certificate Signing Request and displays all fields in human-readable form. Paste your CSR (the block between -----BEGIN CERTIFICATE REQUEST----- and -----END CERTIFICATE REQUEST-----) and the tool shows the subject (CN, O, OU, C, etc.), the public key algorithm and size, SANs if present, and signature algorithm. Use it to verify that a CSR was generated correctly before submitting it to a CA, to troubleshoot errors from the CA (e.g. wrong domain or missing SANs), or to inspect a CSR you received from another team. Decoding is done in-browser and does not require sending the CSR to a server. The tool does not validate the signature or the key; it only parses and displays the contents.
PEM format: base64-encoded CSR with BEGIN/END CERTIFICATE REQUEST lines. Some tools also accept DER or pasted base64.
No. Only the CSR (public part). Never paste your private key into a decoder unless you fully trust the tool and it runs locally.
Common reasons: wrong or missing CN/SAN, unsupported key type or size, or invalid characters. Use the decoder to confirm what you sent.
This tool is for CSRs. Use an SSL certificate decoder to view the contents of an issued certificate.
If the tool runs in-browser only, the CSR stays on your device. Check the tool's documentation to be sure.