Fine‑Tune Nodemon: Watch Only Your src Folder and Skip node_modules & .git

Desired Outcome

When developing a Node.js application, you often want Nodemon to restart the app only when you change source files. Watching the entire project tree—including node_modules and .git—can slow restarts and generate noisy logs. This guide shows how to configure Nodemon to watch just the src directory while ignoring the other two, using a nodemon.json file.

Prerequisites

• Node.js 12+ installed (runtime and npm or yarn)
• Project with a src folder and an entry point (e.g., src/index.js)
• Local Nodemon installation: npm install --save-dev nodemon

Focused Procedure

1. Create nodemon.json in the project root. This file tells Nodemon how to behave.

   {
     "watch": ["src"],
     "ignore": ["node_modules", ".git"],
     "ext": "js,json",
     "exec": "node src/index.js"
   }
   

   • watch lists directories or files to monitor. src is relative to the project root.
   • ignore lists glob patterns that should never trigger a restart. The two entries above prevent any event from node_modules or .git.
   • ext limits the file extensions that trigger a restart. This avoids watching binary assets.
   • exec specifies the command that Nodemon runs. Adjust if your entry point differs.
2. Run Nodemon with the config file.

   npx nodemon --config nodemon.json
   

   Because nodemon.json is in the project root, you can also simply type npx nodemon and Nodemon will automatically pick it up.

Expected Checks

Use the following tests to confirm the configuration is active.

• Basic restart test: Edit src/index.js (or any file inside src). Nodemon should log:

  [nodemon] restarting due to change in /path/to/project/src/index.js
  

• Ignore test: Create a file node_modules/dummy.js and modify it. No restart log should appear.
• Verbose mode: Run npx nodemon --config nodemon.json --verbose. The output should include lines like:

  [nodemon] watching src
  [nodemon] ignoring node_modules, .git
  

• Fallback test: Temporarily rename nodemon.json to nodemon.json.bak and run npx nodemon. Nodemon will revert to its default behavior (watching all files). Editing any file should trigger a restart, confirming the original config was applied.

Recovery Options

If Nodemon behaves unexpectedly, try these steps:

• Validate JSON syntax. Use jsonlint nodemon.json or an online validator to catch stray commas or missing quotes.
• Check path case sensitivity. On Linux, node_modules and .git must match the exact case; on Windows the match is case‑insensitive.
• Verify glob patterns. Nodemon uses minimatch. Ensure patterns are simple directory names; complex patterns may need escaping.
• Inspect the exec command. If Nodemon exits immediately, the exec string may contain a typo. Run the command manually to confirm it works.
• Use --verbose. This flag prints internal events and can reveal why a file change was ignored.

Limitations & Platform Notes

• On macOS, the default file‑system watcher (FSEvents) may still generate events for ignored directories if they are symlinked into src. Avoid symlinks or use --legacy-watch.
• Large node_modules trees on Linux can still cause a spike in events if the kernel’s inotify limit is reached. Increase /proc/sys/fs/inotify/max_user_watches if you notice performance issues.
• Glob patterns are case‑sensitive on Linux but case‑insensitive on Windows. Keep directory names consistent.

Practical Verification Checklist

Check	Command	Expected Result
Run Nodemon	npx nodemon --config nodemon.json	Logs show "watching src" and "ignoring node_modules, .git"
Modify src file	Open src/index.js and change a line	Restarts, log of change path
Modify ignored file	Create/modify node_modules/dummy.js	No restart, no log
Test verbose	npx nodemon --config nodemon.json --verbose	Detailed watch/ignore events

Conclusion

By confining Nodemon’s watch scope to src and ignoring node_modules and .git, you reduce unnecessary restarts and improve developer productivity. The nodemon.json approach keeps configuration declarative and version‑controlled, making it easy to share across team members.