OpenSSL vs an online generator.

OpenSSL is the right tool in CI. A website that asks for your private key is the wrong tool everywhere. A generator that never sees the key is a workshop, not a CA.

What we produce

The same PEM, CSR, and PFX shapes OpenSSL writes. Equivalent commands are on the cheat sheet if you want both.

Generate in the browser when you are on a machine that does not have OpenSSL, or you do not want to fight config files for a one-off SAN.

Written for operators who have to trust the box they just stood up. Private keys stay in the tab. Open the generator.

Self-signed SSL for localhost HTTPS
Fix NET::ERR_CERT_AUTHORITY_INVALID
Trust a self-signed certificate on Windows
Trust a self-signed certificate on macOS