name: capacitor-performance
description: Performance optimization guide for Capacitor apps covering bundle size, rendering, memory, native bridge, and profiling. Use this skill when users need to optimize their app performance.

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
bunx 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

Resources

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