---
title: vmMemoryLimit | Config
outline: deep
---

# vmMemoryLimit

- **Type:** `string | number`
- **Default:** `1 / CPU Cores`

This option affects only `vmForks` and `vmThreads` pools.

Specifies the memory limit for workers before they are recycled. This value heavily depends on your environment, so it's better to specify it manually instead of relying on the default.

::: tip
The implementation is based on Jest's [`workerIdleMemoryLimit`](https://jestjs.io/docs/configuration#workeridlememorylimit-numberstring).

The limit can be specified in a number of different ways and whatever the result is `Math.floor` is used to turn it into an integer value:

- `<= 1` - The value is assumed to be a percentage of system memory. So 0.5 sets the memory limit of the worker to half of the total system memory
- `\> 1` - Assumed to be a fixed byte value. Because of the previous rule if you wanted a value of 1 byte (I don't know why) you could use 1.1.
- With units
  - `50%` - As above, a percentage of total system memory
  - `100KB`, `65MB`, etc - With units to denote a fixed memory limit.
    - `K` / `KB` - Kilobytes (x1000)
    - `KiB` - Kibibytes (x1024)
    - `M` / `MB` - Megabytes
    - `MiB` - Mebibytes
    - `G` / `GB` - Gigabytes
    - `GiB` - Gibibytes
:::

::: warning
Percentage based memory limit [does not work on Linux CircleCI](https://github.com/jestjs/jest/issues/11956#issuecomment-1212925677) workers due to incorrect system memory being reported.
:::