What Tools Did You Build for Yourself?

The Dogma metalanguage: https://dogma-lang.org/

Because BNF-style metalanguages have stagnated over the decades, and can't describe binary structures.

A weather site that shows yesterday's weather: https://weather.bingo/901846663/41061/threeday/f

A (Windows-only) very fast disk-space analysis tool. https://github.com/jasonthorsness/jt-canhasfreespace

both I think I am the only user, but both I keep using :P

a scientific paper reader/organizer https://youtu.be/uU_WeER2PSs

A simple brainstorming tool for coming up with mini project ideas https://brainstorm.gg

A simple invoice creator.