Performance Is a Feature
Users don't wait. A 100ms delay in load time can drop conversion rates measurably. Performance isn't an afterthought -- it's a core feature that directly impacts your product's success.
Next.js gives you excellent defaults, but there's still plenty you can do to push further.
Analyze Your Bundle First
Before optimizing, measure. Use the Next.js bundle analyzer to see exactly what's in your JavaScript bundles. You'll almost always find:
- Large dependencies you could replace with lighter alternatives
- Unused code that's being shipped to the client
- Duplicate packages pulled in by different dependencies
The rule of thumb: if a library is over 50KB gzipped, look for a smaller alternative or consider lazy loading it.
Server Components by Default
React Server Components are the biggest performance win in modern Next.js. They render on the server and send zero JavaScript to the client.
Keep your component tree on the server by default. Only add "use client" when you genuinely need interactivity -- event handlers, state, effects, or browser APIs.
A common pattern: create a thin client wrapper for interactivity and keep the heavy rendering logic in server components.
Image Optimization
Images are typically the largest assets on any page. The Next.js Image component handles most optimization automatically:
- Format conversion -- Serves WebP or AVIF when the browser supports it
- Responsive sizing -- Generates multiple sizes and serves the right one
- Lazy loading -- Only loads images as they enter the viewport
- Blur placeholders -- Shows a blurred preview while loading
Always specify width and height to prevent layout shift, and use the priority prop for above-the-fold images.
Caching Strategies
Next.js provides granular caching controls:
- Static rendering -- Pages rendered at build time and cached at the edge
- ISR (Incremental Static Regeneration) -- Static pages that revalidate on a schedule
- Dynamic rendering -- Server-rendered on every request when needed
Choose the least dynamic option that meets your requirements. A page that changes hourly doesn't need to be dynamic -- ISR with a 1-hour revalidation window works perfectly.
Font Loading
Fonts can block rendering if loaded incorrectly. Use next/font to self-host fonts with automatic optimization:
- Fonts are downloaded at build time and served from your domain
- Zero layout shift with automatic
size-adjust - No external network requests to Google Fonts or other CDNs
Measuring Results
Use Lighthouse, Web Vitals, and real user monitoring to track your improvements. Focus on the Core Web Vitals:
- LCP (Largest Contentful Paint) -- Under 2.5 seconds
- INP (Interaction to Next Paint) -- Under 200 milliseconds
- CLS (Cumulative Layout Shift) -- Under 0.1
Optimize iteratively and always measure the impact of each change.