Engineering
What is ISR (Incremental Static Regeneration)?
ISR is the middle ground between SSG and SSR: generates the static page at build, regenerates in the background after X seconds — CDN speed with near-fresh data.
Invented by Next.js. You set revalidate (e.g., 60 seconds). First request serves static; after that, the next request triggers a background regenerate; new users see the fresh version.
Perfect for pages that change occasionally (prices, popular blog, catalog). CDN speed without being stuck 6 hours with stale data.
Frequently asked questions
Is ISR expensive?
No. Charges compute only on regeneration (once per interval), not per request. Much cheaper than pure SSR.
Does ISR work on any host?
No, requires supporting infra (Vercel is the reference). Pure static hosts no.