Sometimes when a Node.js process runs out of memory while attempting to allocate new objects on the heap you'll into a "FATAL ERROR" message with the details being "Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory".

## What is the heap in Node.js and Javascript?

The heap is a region of memory that is used by Node.js in order to store objects created during the execution of a program. When this memory is full, Node.js attempts to allocate more memory, up to a certain limit.

Once that limit is reached and there is still not enough memory available, the process will throw a "FATAL ERROR" message instead.

The error gets thrown in a variety of situations, to enumerate a few:

1. When attempting to process large amounts of data or execute complex algorithms that require a lot of memory.
2. When running a Node.js server with a large number of connections or concurrent requests.
3. When running a Node.js application in a container or virtual machine with limited memory resources.

## How to fix JavaScript heap out of memory

**Linux/MacOS**

To fix the error on either Linux or MacOS, you can run the below code to set the maximum heap size to 4GB.

```javascript
node --max-old-space-size=4096 server.js
```

Alternatively, if you're using a Docker container to run your Node.js, use this code:

```javascript
docker run -m 4g myapp
```

**Windows**

To fix the same error on Windows installation, follow these steps:

1. Open Command Prompt or PowerShell as an administrator.
2. Navigate to your Node.js application directory using the "cd" command.
3. Run the following command to start your Node.js application with a larger memory limit:

```arduino
node --max-old-space-size=4096 server.js
```

**Conclusion**

Using the above commands you'll be able to fix the JavaScript heap out of memory error on both Linux based operating systems and Windows.

## How Jam can help you debug faster

Running out of heap memory in Node.js can be a challenging problem to debug, especially when you're dealing with complex applications or large data sets. The good news is you can save yourself a lot of time debugging tickets by asking your team to try logging issues with [Jam’s free bug reporting browser extension](/content/?ref=strawberryjam.ghost.io). Jam makes it easy for anyone to create developer-ready bug reports by auto-including [console logs, network requests](/content/tracing?ref=strawberryjam.ghost.io), and [steps to reproduce the issue](/content/blog/launching-today-debug-timeline-you-never-have-to-write-repro-steps-again/?ref=strawberryjam.ghost.io) along with the screen recording.

With Jam, you can capture detailed debug data just by recording your screen. Jam packages it all up into a link you can share, or a [ticket in your issue tracker](/content/docs/integrations/?ref=strawberryjam.ghost.io). Now everyone can log comprehensive bug reports and developers can fix bugs faster without having to follow up.

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