Incremental Static Regeneration (ISR)
Incremental Static Regeneration (ISR) is a Next.js rendering strategy that allows statically generated pages to be updated after deployment, either on a timed schedule or on-demand, without a full rebuild.
ISR gives you the performance of SSG (pre-built HTML from CDN) with the freshness of SSR (updated content). Pages are generated at build time, then revalidated in the background after a specified time interval or when triggered programmatically.
This is ideal for content that changes occasionally — blog posts with updated information, product pages with changing prices, or documentation with periodic updates. Users always see a cached version (fast), while the next visitor after the revalidation window gets a freshly generated page.
In Next.js App Router, use `revalidate` in your fetch options or route segment config. For on-demand revalidation, use `revalidatePath()` or `revalidateTag()` in Server Actions or Route Handlers — perfect for webhook-triggered updates from a CMS.
Example
// Next.js App Router — time-based ISR
// app/blog/[slug]/page.tsx
export const revalidate = 3600; // Revalidate every hour
// On-demand ISR via Route Handler
// app/api/revalidate/route.ts
import { revalidatePath } from "next/cache";
export async function POST(request: Request) {
const { path } = await request.json();
revalidatePath(path);
return Response.json({ revalidated: true });
}Related terms
Static Site Generation (SSG)
Static Site Generation (SSG) is a rendering strategy where pages are pre-rendered as static HTML files at build time, served directly from a CDN without server computation on each request.
Server-Side Rendering (SSR)
Server-side rendering (SSR) is a technique where the web server generates the complete HTML for a page on each request, sending fully rendered content to the browser and search engine crawlers.
Page Speed
Page speed is the measurement of how quickly a web page's content loads and becomes interactive, typically measured by metrics like Time to First Byte (TTFB), First Contentful Paint (FCP), and Largest Contentful Paint (LCP).
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