Quick answer
A single-page application (SPA) loads one page and updates it with code. Gmail is an SPA.
What it is
An SPA loads once, then updates itself without a full reload. Clicking a link swaps the view instead of requesting a new page.
Why it matters
SPAs feel fast because the browser never waits for a fresh document. They suit dashboards and tools, where the user acts after the first load.
How to use it
- Use an SPA when the user interacts after the first load.
- Add server rendering for the first view.
- Use a router that supports deep links and browser history.
- Watch bundle size and memory use.
Examples
- Gmail is an SPA.
- A SaaS dashboard is an SPA.