ISRIncremental Static Regeneration
A hybrid rendering model that serves a cached static page but rebuilds it in the background when it goes stale, giving you SSG speed with SSR freshness.
· Reviewed by senior engineers
Incremental Static Regeneration (ISR) is a hybrid rendering strategy popularised by Next.js. Pages are statically generated at build time but can be regenerated on demand or on a schedule. The CDN keeps serving the cached HTML to users, and a background revalidation refreshes it without blocking the request. The next visitor gets the new version.
ISR solves the central tension of SSG: a fully static site is fast and cheap, but stale data is painful. With ISR you can publish a thousand-page e-commerce site, set a 60-second revalidation window, and get near-real-time freshness with CDN-grade performance. On-demand revalidation goes further — your CMS or PIM can hit a webhook the moment content changes and only the affected pages rebuild.
The pitfalls are subtle. A poorly-set revalidate window can hammer your origin. Stale-while-revalidate means at least one user sees old content after each change, which matters on price or inventory pages. Cache invalidation across regional CDN nodes can lag, so a global launch needs care.
We use ISR routinely on headless commerce builds, content-heavy marketing sites and glossaries where new entries arrive but the index lives for months. It is rarely the wrong answer when paired with on-demand revalidation hooks.