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How do you capture and analyze a heap snapshot to find a memory leak?

Q: How do you capture and analyze a heap snapshot to find a memory leak?

**TL;DR.** Capture a **V8 heap snapshot** with v8.writeHeapSnapshot() (or via the inspector), load it in **Chrome DevTools → Memory**, and **compare** snapshots taken over time under steady load. Object types that keep **growing** between snapshots — held by a retainer path you didn't expect — reveal the leak. snapshot A (baseline) snapshot B (after load) <text class='d-sub' x='291' y='64' text-anchor='

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Understand the problem

Generating and diffing V8 heap snapshots.

nodejsmemoryheap-snapshotdebugging

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Read the code

Dump a snapshot to disk

import v8 from 'node:v8';

// Trigger on a signal so you can capture during a leak in prod:
process.on('SIGUSR2', () => {
  const file = v8.writeHeapSnapshot();   // e.g. Heap.20240101.heapsnapshot
  console.log('wrote', file);            // open in Chrome DevTools → Memory
});
// Or auto-dump near OOM:  node --heapsnapshot-near-heap-limit=2 server.js

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