Glossary
SSR vs SSG vs ISR
Three rendering strategies: server-rendered on each request (SSR), pre-rendered at build (SSG), or pre-rendered and revalidated (ISR).
Definition
Server-Side Rendering (SSR) renders pages on the server on each request — best for personalised or constantly-changing content. Static Site Generation (SSG) renders pages at build time and serves the static HTML — best for content that rarely changes. Incremental Static Regeneration (ISR) is a hybrid: pages are pre-rendered like SSG but revalidate on a schedule or on-demand — best for product catalogues, blog posts and content that updates occasionally. Modern Next.js supports all three (and React Server Components, which extends the model further).
Why it matters
Choosing the wrong rendering strategy is a top cause of slow sites and high hosting bills. Most public pages benefit from SSG or ISR. SSR is reserved for genuinely dynamic content. We choose per route, not per project.
See also
Next.js
Next.js development company — App Router, RSC, SSG/ISR, edge runtime. Storefronts lifted from Lighthouse 42 to 94 on Next.js 14 in production.
Read →Core Web Vitals
Google's standardised performance metrics: LCP (loading), INP (interactivity) and CLS (visual stability).
Read →React Server Components (RSC)
React components that render exclusively on the server, ship no client JavaScript and can stream their output.
Read →Working on SSR vs SSG vs ISR?
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