I used to use "files", initially one markdown file per project. Eventually (when I moved to emacs) .org file.
When I moved to .org - I started writing "notes", "things and URLs" to remember etc. I still do that.
But recently I started to publish them online as my "devnotes". The setup is really simple. I use mkdocs and publish "quick" notes.
These are the things that I would search for online every now and then.
Check this if you are interested.
I also use Google Keep. But that is mostly for "non technical" stuff. An odd address of the hotel, Picture of kid's medicine (better picture than name)