Every developer has done it at least once: accidentally committed a .DS_Store file, a .idea/ folder, or some other machine-specific artifact into a shared repository. A per-project .gitignore helps, but you have to repeat yourself in every repo. The solution is a global .gitignore — a single file that Git applies to every repository on your machine. How Git decides what to ignore Git evaluates ignore rules from three sources, in order of specificity: