# Prerendering > Prerendering is the practice of running a JavaScript app once at build time and saving the resulting HTML for each route as a real file, so that crawlers, AI… Source: https://northerngo.com/glossary/prerendering/ Language: en Updated: 2026-08-28 --- **Prerendering is the practice of running a JavaScript app once at build time and saving the resulting HTML for each route as a real file, so that crawlers, AI fetchers and first-time visitors receive finished markup instead of an empty container that only fills in after scripts execute.** ### How it works in practice A build script starts the app in a headless browser, visits every route in a list, waits for the view to settle, and writes the resulting DOM to `dist//index.html`. The deployed site then contains one real HTML file per page. A visitor gets readable content on the first byte, and the JavaScript bundle still loads afterwards to make the page interactive — the [hydration](/glossary/hydration/) step. The reason to bother is that not every consumer of your pages runs JavaScript. Google does, with a delay and a rendering budget. Bing is inconsistent. Most LLM crawlers, link preview bots and scrapers simply read the HTML they are given. For those, an unrendered [single-page application](/glossary/single-page-application/) has no content at all. ### Prerendering, SSR and SSG are not the same thing The words are used loosely, so it is worth pinning them down: - **Prerendering** happens once, at build time, and produces static files. Content is as fresh as your last deploy. - **Server-side rendering (SSR)** happens per request, on a server, so the HTML can be personalised or up to date. It costs a running server. - **Static site generation (SSG)** is essentially prerendering as the primary architecture rather than a bolt-on to an existing client app. There is also a second, unrelated meaning: browsers use "prerender" for speculatively loading a page the user is likely to visit next. Same word, different subject — context usually makes it obvious which one is meant. ### What to watch out for Prerendering only covers the routes you list, so a new page that nobody added to the list ships as an empty shell. Anything personalised must not be captured in the snapshot — prerendering a logged-in view bakes one user's data into a public file. And the prerendered HTML and the client render need to agree, because if they differ the page will visibly flicker as the app replaces the markup. --- NorthernGo is an AI-powered platform for building production-ready web apps with zero coding. Local AI generation via WebGPU is unlimited and free, and you own all generated source code. https://northerngo.com/