Arduino MemoryFree Library

Overview

On classic Arduino boards like the Uno (ATmega328), you only have 2 KB of RAM. It disappears fast — global variables, the stack, String objects, and Serial.print("...") calls all eat into it. When you run out, the sketch crashes in ways that are nearly impossible to diagnose without a tool like this.

The MemoryFree library lets you call freeMemory() from anywhere in your sketch to get the number of bytes currently available between the heap and the stack. Print it over serial during development and you’ll immediately know if you have a memory leak or are running dangerously close to zero.

The Core Problem

Every time you write Serial.print("some debug message"), that string literal is copied into RAM — not kept in flash. On a device with 2 KB of RAM total, a handful of debug prints can silently eat several hundred bytes. The library solves both sides of this:

• Measure — freeMemory() returns available RAM at any point in time
• Reduce usage — pair it with the F() macro (Arduino IDE 1.0+) to keep string literals in flash: Serial.print(F("hello")) uses zero RAM for the string

Usage

#include <MemoryFree.h>

void setup() {
  Serial.begin(9600);
  Serial.print(F("Free RAM: "));
  Serial.println(freeMemory());
}

void loop() {
  // measure before/after dynamic allocations
}

Important Caveat

Memory is dynamic. The value at setup() reflects static globals, but function calls push stack frames that temporarily reduce available RAM. Leave a safety margin — running at 50–100 bytes free is asking for trouble. A reading of zero means you have already overwritten the heap.

Installation

Available via the Arduino IDE Library Manager — search for MemoryFree — or clone the repository and place the folder in your Arduino/libraries/ directory.