Node.js os.freemem() Method

Last Updated : 10 Aug, 2026

The os.freemem() method in Node.js returns the amount of free system memory in bytes. It helps developers quickly check available RAM and monitor system performance.

  • It is useful for monitoring memory and improving performance.
  • It can be combined with os.totalmem() to understand memory usage.

Syntax:

os.freemem()

Where:

  • os: It is the built-in Node.js module that provides information about the operating system.
  • freemem(): It is a method that returns the amount of free system memory in bytes.

Return Value: It returns the amount of free system memory available in bytes.

Example 1:

javascript 
// Allocating os module
const os = require('os');

// Printing os.freemem() value
console.log(os.freemem());

Output:

4158910464

Example 2:

javascript 
// Allocating os module
const os = require('os');

// Printing os.freemem() value
const free_memory = os.freemem();
const free_mem_in_kb = free_memory / 1024;
const free_mem_in_mb = free_mem_in_kb / 1024;
const free_mem_in_gb = free_mem_in_mb / 1024;

free_mem_in_kb = Math.floor(free_mem_in_kb);
free_mem_in_mb = Math.floor(free_mem_in_mb);
free_mem_in_gb = Math.floor(free_mem_in_gb);

free_mem_in_mb = free_mem_in_mb % 1024;
free_mem_in_kb = free_mem_in_kb % 1024;
free_memory = free_memory % 1024;

console.log("Free memory: " + free_mem_in_gb + "GB "
    + free_mem_in_mb + "MB " + free_mem_in_kb
    + "KB and " + free_memory + "Bytes");

Output:

Free memory: 4GB 110MB 88KB and 0Bytes

Note: The above program will compile and run by using the node index.js command. 

Use Cases of os.freemem() Method

  • It is used to monitor available system memory during application execution.
  • It helps in optimizing performance by checking if enough memory is available before heavy tasks.
  • It is useful in logging and diagnostics to track system resource usage.

Reference: https://nodejs.org/api/os.html#os_os_freemem

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