Caching Strategies
Performance is often just a matter of 'not doing the work'. Learn how browsers, CDNs, and frameworks coordinate to store data as close to the user as possible.
Strategy Details
Next.js handles most of this automatically. By using static rendering (SSG/ISR), your application is globally cached by default.
Hydration Logic
Pre-rendered HTML is sent to the client, then React 'hydrates' it to enable full interactivity.
The Multi-Level Cache
Speed isn't just about rendering; it's about ensuring data never has to travel to the server if someone else has already seen it.
Origin Server
Database & Redis caching. Next.js "fetch()" cache persists here.
Global CDN (Edge)
Cached HTML/Images at locations nearest to users (e.g., Tokyo, NYC).
Browser Memory
Assets stored locally on your device for instant repeat visits.
Global CDN Data
For SSG and ISR pages. Data is Global—the same for every user on earth. This is cached on the Edge Network so it never hits your server.
Personalized Data
Data that belongs to a specific user (Account details, carts). Must Bypass CDN to prevent data leaking between users.
Developer Tools Deep Dive
How to verify your caching strategy using the browser's Network tab.
Inspection: Network Headers
Open your browser DevTools (F12) $\rightarrow$ Network Tab $\rightarrow$ Click a Request $\rightarrow$ Response Headers.
Vercel Note: Next.js automatically sets these headers based on your page configuration (SSG/ISR/SSR).
Architecture Impact
CSS and JS bundles use "immutable" hashes. They stay in the browser cache forever until the filename changes.
The Framework Guarantee
When you use Static Rendering (SSG), Next.js automatically generates the ideal Cache-Control headers for you. You don't need to manually configure CDNs—the framework ensures that your global assets are distributed globally, while your private routes remain private.
CDN caches are invalidated automatically on new deployments.
ISR allows the CDN to serve old data while fetching the new update.
Images and CSS are hashed, allowing infinite browser caching.