# Single-page application (SPA)

> A single-page application loads one HTML document once and then rewrites the page in the browser with JavaScript as the user navigates, instead of requesting…

Source: https://northerngo.com/glossary/single-page-application/
Language: en
Updated: 2026-08-28

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**A single-page application loads one HTML document once and then rewrites the page in the browser with JavaScript as the user navigates, instead of requesting a new document from the server for every view. React, Vue and Svelte apps are single-page applications by default.**

### What the browser actually receives

The server sends a nearly empty HTML file — often little more than `<div id="root"></div>` and a script tag — plus a JavaScript bundle. The bundle boots, reads the URL, renders the right view into that empty div, and takes over the browser's history API so that clicking a link changes the address bar without a full page load.

That buys real things. Navigation feels instant because only data moves, not a whole document. State survives between views, so a half-filled form or an open sidebar does not reset. It is the natural architecture for anything that behaves like an application rather than a document: dashboards, editors, booking flows.

### The costs people underestimate

**Nothing exists until the JavaScript runs.** The first paint is delayed by download, parse and execution of the bundle, which is why SPAs so often have poor [Largest Contentful Paint](/glossary/core-web-vitals/) on mid-range phones.

**Crawlers and AI fetchers may see the empty div.** Google renders JavaScript, eventually and with a budget. Many other consumers — most LLM crawlers, link preview bots, some social scrapers — fetch the raw HTML and never execute a script. If the content only exists after render, to them the page is blank. The usual fix is [prerendering](/glossary/prerendering/) or server rendering the routes that need to be found.

**Routing has to be handled on the server too.** Deep-linking to `/pricing` returns a 404 unless the host is configured to serve `index.html` for unknown paths.

### The misconception

"Single-page" describes how the app is delivered, not how it looks. A single-page application can have a hundred distinct URLs and views; the point is that they are produced in the browser rather than fetched as separate documents. Conversely, a site with one physical page and no routing is not what anyone means by an SPA.

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