# Fix 'EMFILE: too many open files, watch' in React Native

> Learn how to fix the EMFILE too many open files watch error in React Native on macOS by installing the watchman utility with Homebrew.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2020-10-22 | Updated: 2026-08-07 | Topics: [React Native](https://flaviocopes.com/tags/react-native/) | Canonical: https://flaviocopes.com/react-native-emfile-too-many-open-files/

The `EMFILE: too many open files, watch` error in React Native on macOS is fixed by installing **watchman** with Homebrew. Here's the story, and why it works.

I was starting a [React](https://flaviocopes.com/react/) Native project on my MacBook Air but when running the command:

```bash
npx react-native start
```

I got an error that contained this line:

```
Error: EMFILE: too many open files, watch
```

## Why does this error happen?

That command starts Metro, the React Native bundler. To provide hot reloading, Metro watches every file in your project for changes, and a React Native project contains thousands of files once you count `node_modules`.

Without a better tool available, Metro falls back on Node's built-in file watching, which keeps a file descriptor open for each watched file. macOS puts a fairly low limit on how many files a process can hold open at once. Cross that limit and the operating system refuses to open more, which surfaces as `EMFILE: too many open files`.

So the error is not about your code. It's the file watcher running out of a system resource.

## The fix: install watchman

I tried various ways to solve it, until I found the suggestion to install the `watchman` utility using [Homebrew](https://flaviocopes.com/homebrew/).

I ran

```bash
brew install watchman
```

and that fixed the problem, because React Native internally was able to use `watchman` to watch file changes (used to provide hot reloading in the app to refresh it when a file is changed).

`watchman` is a file watching service built by Facebook, the same company behind React Native, and Metro picks it up automatically when it's installed. No configuration needed.

It's much more efficient than the built-in file watching: it runs as a single background service that watches whole directory trees, instead of holding one file descriptor per file. That's why the error disappears.

After installing, stop Metro and run `npx react-native start` again so it detects watchman.

## Still seeing the error?

If the error comes back after the install, watchman may have stale state from previous runs. Clear it with:

```bash
watchman watch-del-all
```

then start Metro again.

You'll find suggestions online to raise the open files limit with `ulimit` instead. That can work, but it treats the symptom. Installing watchman removes the cause, and it makes file watching faster too.