Term · Web & development
Single-page application (SPA)
A single-page application (SPA) is a web application that loads one HTML page and then updates what the user sees with JavaScript, fetching data from the server as needed, instead of loading a new page from the server for each click. Navigation feels fast and app-like.
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Explained
Where SPAs shine
- Dashboards, admin panels and internal tools.
- Customer portals and applications behind a login.
- Interfaces with many interactions on one screen: filters, editors, real-time updates.
The SEO catch
A pure client-rendered SPA sends a nearly empty HTML page; content appears only after JavaScript runs. Google can render JavaScript, but with delays and limits; many other crawlers — some search engines, social media previews and AI crawlers — read only the initial HTML. Public pages built as a pure SPA may be poorly indexed or not indexed at all.
Solutions include server-side rendering, static generation and prerendering, which deliver complete HTML while keeping app-like navigation. See SPA vs server rendering and technical SEO.
Performance
SPAs can load a large amount of JavaScript upfront, which slows the first screen on mid-range phones. Code splitting — loading only what each screen needs — reduces this.
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FAQ
Frequently asked questions
Is an SPA the same as a PWA?
No. An SPA describes how navigation works; a progressive web app describes installability and offline capabilities. A PWA is often built as an SPA.
Are SPAs bad for SEO?
Pure client-side rendering is risky for public pages. With prerendering or server rendering, SPAs can be fully indexable.