Paste or upload a certificate signing request to check the subject, public key, signature algorithm, and any Subject Alternative Names before you submit it to a Certificate Authority.
Runs entirely in your browser — nothing you paste or upload is sent anywhereA CSR only contains public information — your public key and the identity details you're requesting. It's safe to paste here for a quick sanity check before sending it onward.
The decoder reads the fields already present in the CSR — it does not contact a CA or verify anything against the outside world.
Think of a CSR as an application form: it states who you are, which domain names you want covered, and includes your public key so the Certificate Authority can build a certificate around it. It never contains your private key.
Decoding your CSR first lets you confirm the subject name and Subject Alternative Names are exactly right. Fixing a typo here is free; fixing it after a certificate has been issued usually means requesting a replacement.
After the CA returns a signed certificate, use the Certificate & CSR Validator to confirm the certificate was built from this exact request.