Server-side rendering (SSR) is a technique used in web development where the server generates the HTML for a web page, including its initial state and content, and sends that HTML to the client. This is in contrast to traditional client-side rendering (CSR), where the browser loads a minimal HTML file and then JavaScript is executed on the client side to render and update the content.

Vue Server Renderer (vue-server-renderer) is a part of the Vue.js framework that allows you to perform server-side rendering with Vue.js. Vue.js is a progressive JavaScript framework for building user interfaces, and it's commonly used for building single-page applications (SPAs). When you use Vue Server Renderer, the Vue components are rendered on the server before being sent to the client, allowing search engines and browsers without JavaScript support to view the fully rendered page.

Here's a basic overview of how Vue Server Renderer works:

1. Component Rendering on the Server:
   • The server receives a request for a specific URL.
   • It then renders the Vue components associated with that URL on the server.
   • The state of the components, including data and DOM structure, is generated on the server.
2. Sending Rendered HTML to the Client:
   • The server sends the fully rendered HTML to the client as the initial response.
3. Hydration on the Client:
   • When the client receives the HTML, it also loads the Vue.js JavaScript bundle.
   • Vue.js on the client takes over and "hydrates" the rendered HTML. This means attaching event listeners and other client-side functionality to the already rendered DOM.

The key advantages of server-side rendering with Vue.js include improved search engine optimization (SEO) since search engines can easily index the content, and faster time to first paint for users, as they receive a fully rendered page from the server.

It's worth noting that while SSR can offer advantages, it also introduces additional complexity compared to client-side rendering. Developers need to manage both server and client-side code, handle data synchronization, and be mindful of potential performance considerations.