This error means the app ran out of memory. Increasing memory or optimizing code often resolves it.

A 'Heap out of memory' error in Node.js occurs when the application tries to use more memory than the allocated heap space. This often signals inefficient memory management, such as large arrays or objects, or excessive recursion. Increasing the heap memory limit using node --max-old-space-size=4096 (setting 4096 MB, for example) can offer a temporary fix, but it’s crucial to investigate underlying causes. Profiling the app for memory leaks can reveal if objects are being retained in memory unnecessarily, especially with event listeners or global variables that aren’t cleared. Rewriting memory-heavy operations, like large JSON parsing or recursive functions, to use streams or iterative processes can also reduce memory footprint. Caching too much data or inefficiently managing resources can further strain memory; consider limiting the size of in-memory caches and clearing unused data as necessary. Tools like Chrome DevTools, heapdump, and clinic.js can capture memory snapshots, helping you trace high-usage areas. Ultimately, fixing a 'Heap out of memory' error requires addressing inefficiencies in code to avoid exceeding available memory.