Node.js ERR_WORKER_OUT_OF_MEMORY - Fix Worker Terminated by Memory Limit

ERR_WORKER_OUT_OF_MEMORY is the specific error a parent thread receives when a Worker exceeds the heap ceiling set by its own resourceLimits (or the implicit default). It is distinct from a plain heap crash because the limit it hit was configured on the worker, not via NODE_OPTIONS.

What this error means

The main thread catches an error event with code ERR_WORKER_OUT_OF_MEMORY and a message that the worker was terminated for reaching its memory limit. The parent process itself never crashed - a resourceLimits.maxOldGenerationSizeMb you set (or the default) was too small for the worker’s workload.

Node output

Error [ERR_WORKER_OUT_OF_MEMORY]: Worker terminated due to reaching
memory limit: JS heap out of memory
    at [kOnExit] (node:internal/worker)
    at Worker.<computed>.onexit (node:internal/worker)
    code: 'ERR_WORKER_OUT_OF_MEMORY'

Common causes

resourceLimits set too low for the worker

A Worker created with a small maxOldGenerationSizeMb hits that ceiling and is terminated, surfacing this code to the parent - even though the parent had plenty of headroom.

The implicit per-worker default is too small

Without explicit resourceLimits, a worker still has a finite heap. A memory-heavy task (parsing, image work, large buffers) can exceed it.

How to fix it

Raise the worker’s resourceLimits

Give the Worker an explicit, larger old-generation ceiling.

JavaScript

const { Worker } = require('node:worker_threads')
new Worker('./task.js', {
  resourceLimits: { maxOldGenerationSizeMb: 2048 },
})

Shrink the worker’s footprint

Stream or chunk large inputs instead of materializing them in the worker heap.
Lower the number of workers running at once.
Move the limit into the worker’s own execArgv (--max-old-space-size) if you spawn it that way.

How to prevent it

Set worker resourceLimits deliberately, sized to the runner.
Cap worker-pool concurrency in CI.
Process large data incrementally inside workers.