Server-Side Rendering (SSR)
Short definition
Server-side rendering means a page's HTML is built on the server rather than in the browser, then sent to the visitor ready to display.
When a request arrives, the server gathers the needed data, builds the page's full HTML there and then, and sends it to the browser; the browser meets visible content straight away instead of filling an empty shell. Frameworks such as Next.js manage this per page.
You meet it on frequently changing content, such as stock levels or pages personalised for a logged-in user, where data needs to be fresh on every request.
It is often confused with static site generation (SSG). SSG builds a page once in advance and serves it as a file, while SSR rebuilds it on every request, so it stays current but places more load on the server.
The most common mistake is building rarely changing pages, such as an about page or a service description, with SSR as well, which creates unnecessary server load on every request and stretches time to first byte. The correct approach is to reserve SSR for pages that genuinely need fresh data on each visit and use static generation or cached rendering for everything else.
Why it matters
Search engines and social media bots read and preview a page correctly when it arrives already filled with content. SSR strengthens both SEO and the first impression, particularly on pages that change often.
Illustrative example
A flooring manufacturer's stock and pricing page is rebuilt on the server on every visit, so search engines always see current stock information.
