The difficulty of converting an existing Vue.js app to use Nuxt.js SSR (Server-Side Rendering) depends on several factors such as the complexity of the app, the size of the codebase, and the familiarity of the developer with Nuxt.js. Here are some general factors to consider:
That being said, Nuxt.js is designed to make the process of adding SSR to an existing Vue.js app as straightforward as possible. The framework provides a lot of built-in functionality to help developers get started quickly, including automatic code splitting, server-side rendering of pages, and preloading of assets.
If the app is relatively simple and the developer is already familiar with Vue.js and Nuxt.js, it could be possible to convert the app to use SSR in a matter of days. However, for larger and more complex apps, the conversion process could take several weeks or even months. Ultimately, the best way to determine the difficulty of converting an existing Vue.js app to use Nuxt.js SSR is to assess the specific app and project requirements and consult with experienced Nuxt.js developers.