.gitignore File — Git Ignore Rules

GITIGNORE files specify intentionally untracked files and directories that Git should ignore when scanning for changes. Each line in a .gitignore file contains a glob pattern that matches file paths — patterns can include wildcards (*), directory indicators (/), negation (!), and double-star globbing (**) for recursive directory matching. Git checks .gitignore files at every level of the repository, with more specific rules overriding general ones. Common patterns include ignoring build output (dist/, build/), dependencies (node_modules/, vendor/), environment files (.env), IDE configuration (.idea/, .vscode/), OS-generated files (.DS_Store, Thumbs.db), and compiled artifacts (*.o, *.pyc). A global gitignore file (~/.gitignore_global) can be configured for patterns that should be ignored across all repositories on a system. The .gitignore mechanism is critical for keeping repositories clean, preventing secrets from being committed, reducing repository size, and avoiding merge conflicts from generated files. GitHub maintains a comprehensive collection of .gitignore templates for virtually every programming language and framework at github.com/github/gitignore, which many tools (including GitHub's repository creation) offer as starting templates.