EMFILE in Node.js — What It Means and How to Fix It

EMFILE means the process hit the operating system's limit on open file descriptors.

What it means and why it happens

Typical causes: opening thousands of files at once, leaking streams, or file watchers in large projects.

Read the full message: it names the file and line where the problem was detected, which is the best place to start.

What you see

Practical examples

Code that triggers it

await Promise.all(files.map(f => fs.promises.readFile(f)))   // thousands at once

The fix

import pLimit from 'p-limit'
const limit = pLimit(50)
await Promise.all(files.map(f => limit(() => fs.promises.readFile(f))))

Raise the limit

ulimit -n 65536
# or use graceful-fs in your project

Common mistakes

• Unbounded parallelism.
• Not closing streams.
• Many watchers (webpack/jest).

Key takeaways

• EMFILE: EMFILE means the process hit the operating system's limit on open file descriptors.
• Read the message and the line number first.
• Fix the cause, don't just silence the error.

FAQ

How do I check the limit?

ulimit -n.

How do I find which line caused EMFILE?

The error message and stack trace show the file and line; start there and work backwards.