What is a SPA (Single Page Application)?

A SPA (Single Page Application) is a single-page web application that loads once and then dynamically updates the content on the page without a full reload. Instead of requesting a new HTML page from the server every time, a SPA loads only the data and partially updates the interface.

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#How it works

• on first load, the base HTML + JS + CSS is loaded
• further user actions (navigation, clicks) trigger AJAX / Fetch / Web API requests
• the server returns only data (for example, JSON)
• the interface updates via JavaScript right in the browser

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#What this provides

• fast navigation without a page reload
• smooth UX, similar to mobile apps
• less traffic, since only data arrives, not the whole HTML

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#Where it's used

• online services
• personal dashboards
• admin panels
• social networks (Facebook), email clients (Gmail)

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#In one sentence

A SPA is an application that runs in the browser like a full-fledged program, updating only the necessary parts of the page instead of reloading it completely.