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Server Side Rendering

Server-Side Rendering (SSR) means that some parts of your application code can run on both the server and the client. For React this means that you can render your components directly to HTML on the server side (e.g. via a node.js server), which allows for better search engine optimization (SEO) and gives a faster initial response, especially on mobile devices.

The browser typically receives a static HTML site and starts updating the UI immediately; React's bundle code will be downloaded asynchronously and when it completes, the client-side JavaScript will take over via React's hydrate functionality. In the JavaScript ecosystem this is also known as an "isomorphic" or "universal" app.

Why use SSR?


  • Better SEO support, as web crawlers will directly see the fully rendered HTML page.
  • Faster time-to-content, especially on slow internet connections or devices.


  • Some development constraints. Browser-specific code requires some compiler directives to be ignored when running on the server.
  • Increased complexity of build and deployment processes.
  • Increased server-side load.


In SAFE, SSR can be done using fable-react. Its approach is a little different from those you might have seen in the JavaScript ecosystem, as it takes a purely F# approach: you render your Elmish views directly on .NET Core, with all the benefits of the .NET Core runtime.

Further reading