What are Single Page Applications (SPA)? How does Angular support SPAs?

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A Single Page Application (SPA) loads one HTML page on first request and updates parts of the DOM as the user navigates — no full-page reloads. Routing happens in the browser. How Angular supports SPA — Angular Router intercepts URL changes via the browser History API and renders matching components without server round-trips. Faster transitions — only data changes; chrome (header/sidebar) stays mounted. Lazy loading — load route modules on demand; smaller initial bundle. Client-side state — survives across &ldquo;pages&rdquo; without re-fetching. SEO trade-off — pure SPAs ship empty HTML; use Angular Universal for server-side rendering when SEO matters. Deep linking — every URL maps to app state; users can bookmark and share. SPA = one HTML page; the client-side router swaps DOM regions. The trade-off is SEO — mitigate with SSR (`@angular/ssr` in Angular 17+).