𝗛𝗼𝘄 𝘁𝗼 𝗥𝗲𝗱𝘂𝗰𝗲 𝗬𝗼𝘂𝗿 𝗝𝗮𝘃𝗮𝗦𝗰𝗿𝗶𝗽𝘁 𝗕𝘂𝗻𝗱𝗹𝗲 𝗦𝗶𝘇𝗲 𝗯𝘆 𝟳𝟬%
Most web applications ship too much code. The average web page loads 1.7 MB of JavaScript. Developers only use about 35% of the code they deploy.
Small bundles improve your Core Web Vitals. You get faster Largest Contentful Paint and faster Time to Interactive scores.
Follow these 10 steps to shrink your bundle size:
- Tree shaking: Removes unused code. Use ES Module syntax to make this work.
- Code splitting: Breaks your code into smaller pieces.
- Dynamic imports: Load code only when a user needs it.
- Image optimization: Use URL-based transforms instead of large libraries.
- Dependency auditing: Swap heavy libraries for light ones.
- Minification: Shrink your code files.
- Compression: Use Brotli for better results than Gzip.
- Dead code elimination: Remove unreachable code branches.
- Lazy loading: Defer non-critical components.
- Polyfill pruning: Ship only the polyfills your users need.
Three techniques work best together. Lazy loading, polyfill pruning, and dead code elimination can reduce your size by 15-30%.
Audit your dependencies before you install them. Use npx bundle-phobia to check sizes.
For example: • date-fns (13KB) is better than moment.js (67KB). • dayjs (2KB) is a great alternative for date formatting. • Use lodash-es instead of the full lodash library.
Check your progress with these targets: • Total JS size: Aim for under 120 KB. • LCP: Aim for under 2.5s. • TTI: Aim for under 3.5s.
Avoid these mistakes: • Deploying development builds instead of production builds. • Importing entire libraries when you only need one function. • Forgetting to enable Brotli compression on your server.
If you use tree shaking, code splitting, and dependency auditing, you can reduce your payload by 50-70% in one sprint.
Source: https://dev.to/kui_luo/how-to-reduce-your-javascript-bundle-size-by-70-in-10-steps-3j1g