I have just dumped code into a Chrome console and saved a cert while in a pinch. It’s not best practices of course, but when you need something fast for one-time use, it’s nice to have something immediately available.

You could make your own webpage that works in the browser (no backend) and make a cert. I haven’t published anything publicly because you really shouldn’t dump private keys in unknown websites, but nothing is stopping you from making your own.

That’s what NodeJS and Deno are.

The point of the browser support means it runs on modern Web technologies and doesn’t need external binaries (eg: OpenSSL). It can literally run on any JS, even a browser.

Just going to mention my zero-dependency ACME (Let’s Encrypt) library: https://github.com/clshortfuse/acmejs

It runs on Chrome, Safari, FireFox, Deno, and NodeJS.

I use it to spin up my wildcard and HTTP certificates. I’ve personally automated it by having the certificate upload to S3 buckets and AWS Certificates. I wrote a helper for Name.com for DNS validation. For HTTP validation, I use HTTP PUT.