FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory
The V8 heap hit its limit — a large build (webpack, tsc, Next.js) needs more memory, or the app leaks.
Exact message you may see
JavaScript heap out of memoryReached heap limit Allocation failedIneffective mark-compacts near heap limit Meaning
Node caps the heap (roughly 2–4 GB depending on version and system memory). Builds of large projects and memory leaks in long-running servers both hit it.
Common causes
- Large frontend/TypeScript builds
- Memory leak (growing caches, listeners, global arrays)
- Loading huge JSON/files into memory
- Container memory smaller than the heap limit
⚡ Quick fix
- Raise the heap:
NODE_OPTIONS=--max-old-space-size=4096 - Stream large files instead of reading them whole
- Take heap snapshots to find leaks
- Keep the heap limit below the container limit
Detailed fix by platform
Node.js
- Raise heap for a build:bash
NODE_OPTIONS=--max-old-space-size=4096 npm run build node --inspect app.js # then Chrome DevTools → Memory → heap snapshots to find leaks
How to diagnose
- Phase — Build or runtime?
- Growth — Memory grows steadily (leak) or spikes?
- Limits — Heap vs container memory
🔧 Still not fixed?
Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:
Similar errors
Most viewed in Node.js
Other ways to find it
Where this error sits
Origin: Application & API. Errors that are often confused with or caused by this one (click to open):
🧠 Still stuck? Analyze your error
Paste the full message, response headers or stack trace — we'll detect the platform and point to the most likely cause.
💬 What worked for others
No tips yet — did something else fix this for you?
Share what worked for you
Tips are checked by an editor before they appear. Links are removed.
Did this fix work for you?
Report a correction or suggest an improvement
Last updated 9 Oct 2026