# Using Vue in Markdown ## Browser API Access Restrictions Because VuePress applications are server-rendered in Node.js when generating static builds, any Vue usage must conform to the [universal code requirements](https://ssr.vuejs.org/en/universal.html). In short, make sure to only access Browser / DOM APIs in `beforeMount` or `mounted` hooks. If you are using or demoing components that are not SSR friendly (for example containing custom directives), you can wrap them inside the built-in `` component: ## VuePress is composed of two parts: a [minimalistic static site generator](https://github.com/vuejs/vuepress/tree/master/packages/%40vuepress/core) with a Vue-powered [theming system](https://v1.vuepress.vuejs.org/theme/) and [Plugin API](https://v1.vuepress.vuejs.org/plugin/), and a [default theme](https://v1.vuepress.vuejs.org/theme/default-theme-config.html) optimized for writing technical documentation. It was created to support the documentation needs of Vue's own sub projects. Each page generated by VuePress has its own pre-rendered static HTML, providing great loading performance and is SEO-friendly. Once the page is loaded, however, Vue takes over the static content and turns it into a full Single-Page Application (SPA). Additional pages are fetched on demand as the user navigates around the site.