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What is a .gitignore file, and what belongs in it?

Git & SDLC Fundamentals Basic Fresher Conceptual 1 min read

Quick Answer

.gitignore lists file patterns Git should not track — build output (bin/, obj/), dependencies (node_modules/), IDE files (.vs/, .idea/), logs, and secrets / local config (appsettings.Development.json if it holds credentials, .env). If a file is already tracked, adding it to .gitignore does nothing — use git rm --cached.

.gitignore tells Git which files to leave alone — compiled output like bin and obj, node_modules, IDE folders, log files, and anything with secrets like a local .env. The gotcha people hit is that if a file is already committed, adding it to .gitignore won't untrack it — you have to git rm --cached it. And OS-level junk like .DS_Store goes in a global gitignore on my machine rather than every project's file.

  • Start from the language template (GitHub maintains a good VisualStudio.gitignore).
  • A global gitignore (~/.gitignore_global) is for machine/OS files (.DS_Store, Thumbs.db) that shouldn't clutter every repo's file.
  • Never commit secrets — if you already did, rotate them; removing them from history is hard and the old commit is still out there.
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