Introduction to SSR
Server side rendering is a generation HTML code from Svelte application on the Node.js server side, allowing you to respond to a browser request with ready-made code.
Development rules for using SSR
You must understand that your application should behave it is the same in two environments at once: in the browser and in Node.js. To do this, you need to take into account the peculiarities of the environments (for example, Node.js does not have a global Window object).
In other words, you need to write universal code. As for example, you can look at the sources of this application.
SSR in Svelte Easyroute
Using this router, you will be able to set up rendering to server side without too much difficulty. Separate advantage - availability of navigation hooks in which you can load data for Svelte components on the server side, and give the client a ready-made code with data.