I recently published SelfCertForge, an open source desktop app for creating and managing self-signed certificates on macOS and Windows:
https://github.com/rbonestell/SelfCertForge/
I know, I know... this isn't an earth-shattering invention. This came from a place of years of personal annoyance. I’ve been maintaining scripts that wrapped OpenSSL for local certificate workflows: create a long-lived root cert, add it to the trust store, then generate and sign child certificates for local services.
The scripts work but the workflow was clunky. Used infrequently enough that it's easy to forget the flags, not much easier to explain to anyone than OpenSSL itself, and irritating to repeat across machines. Every time I'd share them with colleagues and friends there were always questions and feature requests, so I used Claude Code to amplify my UI/UX design skills (well, I can't amplify 0...) and turned the functionality into a cross-platform GUI.
SelfCertForge can generate root CAs and add them to the system's trust store, generate and sign child certificates, and export DER, PEM, PFX, and P7B formats. It also supports common X.509 fields like Subject, SANs, and Key Usage.
Very important caveat: this is not suitable for production environments or public-facing SSL/TLS.