Performance Optimization for Capacitor

Make your Capacitor apps fast and responsive.

When to Use This Skill

• User has slow app
• User wants to optimize
• User has memory issues
• User needs profiling
• User has janky animations

Quick Wins

1. Lazy Load Plugins

// BAD - All plugins loaded at startup
import { Camera } from '@capacitor/camera';
import { Filesystem } from '@capacitor/filesystem';
import { Geolocation } from '@capacitor/geolocation';

// GOOD - Load when needed
async function takePhoto() {
  const { Camera } = await import('@capacitor/camera');
  return Camera.getPhoto({ quality: 90 });
}

2. Reduce Bundle Size

# Analyze bundle
npx vite-bundle-visualizer

# Tree-shake imports
import { specific } from 'large-library';  // Good
import * as everything from 'large-library'; // Bad

3. Optimize Images

// Use appropriate quality
const photo = await Camera.getPhoto({
  quality: 80,        // Not 100
  width: 1024,        // Limit size
  resultType: CameraResultType.Uri,  // Not Base64
});

// Lazy load images
<img loading="lazy" src={url} />

4. Minimize Bridge Calls

// BAD - Multiple bridge calls
for (const item of items) {
  await Storage.set({ key: item.id, value: item.data });
}

// GOOD - Single call with batch
await Storage.set({
  key: 'items',
  value: JSON.stringify(items),
});

Rendering Performance

Use CSS Transforms

/* GPU accelerated */
.animated {
  transform: translateX(100px);
  will-change: transform;
}

/* Avoid - triggers layout */
.animated {
  left: 100px;
}

Virtual Scrolling

// Use virtual list for long lists
import { VirtualScroller } from 'your-framework';

<VirtualScroller
  items={items}
  itemHeight={60}
  renderItem={(item) => <ListItem item={item} />}
/>

Debounce Events

import { debounce } from 'lodash-es';

const handleScroll = debounce((e) => {
  // Handle scroll
}, 16); // ~60fps

Memory Management

Cleanup Listeners

import { App } from '@capacitor/app';

// Store listener handle
const handle = await App.addListener('appStateChange', callback);

// Cleanup on unmount
onUnmount(() => {
  handle.remove();
});

Avoid Memory Leaks

// Clear large data when done
let largeData = await fetchLargeData();
processData(largeData);
largeData = null; // Allow GC

Profiling

Chrome DevTools

1. Connect via chrome://inspect
2. Performance tab > Record
3. Analyze flame chart

Xcode Instruments

1. Product > Profile
2. Choose Time Profiler
3. Analyze hot paths

Android Profiler

1. View > Tool Windows > Profiler
2. Select CPU/Memory/Network
3. Record and analyze

Metrics to Track

Metric	Target
First Paint	< 1s
Time to Interactive	< 3s
Frame Rate	60fps
Memory	Stable, no growth
Bundle Size	< 500KB gzipped

Resources

• Chrome DevTools: https://developer.chrome.com/docs/devtools
• Xcode Instruments: https://developer.apple.com/instruments