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Development

Incremental Static Regeneration

ISR

Portrait of Lukas Horvath, co-founder of Roelu Studio
Lukas HorvathCo-founder

What is Incremental Static Regeneration?

Incremental static regeneration, usually shortened to ISR, is a hybrid rendering strategy where pages are served as static files but can be rebuilt individually in the background after the site has been deployed. Incremental static regeneration lets a site stay as fast as a fully static one while still picking up content changes within seconds. The technique was popularized by Next.js and now exists in most modern frameworks.

Why it matters

Pure static sites are fast but force a full rebuild for every content change. On a small site that is fine. On a site with ten thousand pages, every rebuild takes ten minutes, and the marketing team starts to feel it. ISR fixes that. The team publishes a blog post in Sanity, and within seconds that specific page rebuilds in the background — without touching the other 9,999. The visitor gets static-speed performance. The marketer gets near-instant publishing. It is the answer to the old trade-off between speed and freshness, and it is why most large content sites built on Next.js use it by default.

How it works

The site is built once as a set of static pages and deployed to a CDN. Each page is tagged with a revalidation rule — either a time interval (refresh every 60 seconds) or a webhook trigger (refresh when this content changes in the CMS). When a visitor requests a page, the CDN serves the cached version instantly. In the background, if the revalidation rule has fired, the framework rebuilds that page using fresh data and quietly replaces the cached copy. The next visitor gets the new version. No full redeploy, no waiting. From the marketer's side it feels like normal publishing. From the visitor's side every page still loads in milliseconds.

Related terms

  • Static Site Generation

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    Building every page of a website in advance, once, and storing the result as plain files ready to ship from a CDN. The output is a site that loads in…

  • Server-Side Rendering

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    When a website builds the page on the server before sending it to the visitor's browser. The visitor sees finished content immediately, and Google sees the…

  • Next.js

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    A modern web framework for building fast, search-friendly websites and apps in React. It is the default choice for serious scale-up sites where speed, SEO, and…

  • Vercel

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    The hosting and deployment platform built by the same team that builds Next.js. It runs the build pipeline, the global CDN, the preview URLs, and the analytics…

  • Caching

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    Storing a copy of a page, image, or piece of data so it can be served instantly the next time it's requested — instead of regenerating it from scratch on every…

  • Headless CMS

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    A content management system that separates where content is stored from how it's shown, giving marketers a place to publish without rebuilding the front-end…

  • Draft Mode

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    A CMS feature that lets editors save and preview unpublished content on the actual live site before it goes public, so the team sees exactly what visitors will…