The Signal Amplification Technique

Memory leaks in React often stem from event listeners, timers, or subscriptions that persist after component unmount. A single mount-unmount cycle might leak just 1-2 MB, making it difficult to distinguish from normal garbage collection noise. By repeating the interaction 10-20 times, the leak signal amplifies proportionally. If each cycle leaks 1.5 MB, twenty cycles produce a 30 MB delta that stands out clearly after forced garbage collection.

Baseline and Comparison Workflow

The profiling process relies on establishing a clean baseline before triggering suspected leaks. Open Chrome DevTools Memory tab, force Garbage Collection (GC) using the trash icon, and capture an initial snapshot. Next, perform repetitive actions like navigating routes or toggling modals 10-20 times to stress test the component lifecycle. Force garbage collection again to eliminate temporary allocations. Finally, take a comparison snapshot and examine the Size Delta column in Comparison view.

Snapshot Analysis Pattern

Baseline Snapshot:     45 MB (clean state)
After 20 Interactions: 85 MB (temporary + leaked)
After Forced GC:       75 MB (30 MB retained)

In this example, the 30 MB difference reveals retained objects. Sort by Size Delta and inspect the Retainers panel to trace the reference chain. Common culprits include "document" references holding event listeners, "Window" objects with global variables, or third-party library caches pointing to unmounted components.

Programmatic Memory Monitoring

For automated leak detection during development, the "performance.memory" API provides heap size metrics. After forcing garbage collection and waiting for stabilization, capture baseline "usedJSHeapSize". Execute the repetitive interaction loop, force another garbage collection cycle, and compare the final heap size. A persistent increase indicates objects not being released, while a return to baseline confirms proper cleanup.

Automated Leak Detection Code

// Development-only memory leak detector
if (performance.gc) {
  performance.gc();
  await new Promise(resolve => setTimeout(resolve, 1000));
  
  const baseline = performance.memory.usedJSHeapSize;
  console.log('Baseline:', baseline);
  
  for (let i = 0; i < 20; i++) {
    // Mount/unmount component or trigger action
  }
  
  performance.gc();
  await new Promise(resolve => setTimeout(resolve, 1000));
  
  const after = performance.memory.usedJSHeapSize;
  console.log('Leaked:', after - baseline, 'bytes');
}

Applied Insight

Use this repetitive profiling technique when suspecting lifecycle-related leaks in React applications. The amplification approach makes subtle leaks visible by converting per-cycle drips into measurable pools. Focus on routes, modals, and subscriptions with mount-unmount patterns. Always force garbage collection between snapshots to isolate retained objects from temporary allocations.