Ignoring Files with .gitignore

Not every file in your project should be committed.

Some files are generated, local, huge, or secret.

.gitignore tells Git:

Do not track these files by default.

Common files to ignore

For a Node.js project:

node_modules/
dist/
.env
.DS_Store
npm-debug.log*

Why?

• node_modules/ can be reinstalled from package.json.
• dist/ is build output.
• .env often contains secrets.
• .DS_Store is a macOS local file.
• log files are local noise.

.gitignore does not remove already tracked files

This is a common beginner surprise.

If config.env is already tracked by Git, adding it to .gitignore does not automatically remove it from Git history.

To stop tracking it:

git rm --cached config.env

Then commit the change:

git commit -m "Stop tracking local environment file"

The file stays on your machine, but Git stops tracking it.

Do not commit secrets

Never commit:

• API keys,
• database passwords,
• private keys,
• production credentials,
• access tokens.

If a secret is pushed to GitHub, assume it is exposed.

Rotate the secret. Do not only delete it from the latest commit.

Example .gitignore for backend app

# dependencies
node_modules/

# build output
dist/
build/

# environment
.env
.env.local

# logs
*.log

# editor/system
.vscode/
.DS_Store

Some teams commit .vscode/settings.json intentionally. That is fine if the team agrees. The rule is not "always ignore everything local"; the rule is "commit only files that help the project".

Interview answer

.gitignore defines patterns for files Git should not track, such as dependencies, build output, logs, and local environment files. It only affects untracked files. If a file is already tracked, I need to remove it from the index with git rm --cached before .gitignore will stop future tracking.