docs: clarify that SSR is required for SSG with content (#14560)

Author: th0rgall

documentation/docs/20-core-concepts/40-page-options.md

@@ -117,15 +117,17 @@ export const prerender = true;
 
 ## ssr
 
-Normally, SvelteKit renders your page on the server first and sends that HTML to the client where it's [hydrated](glossary#Hydration). If you set `ssr` to `false`, it renders an empty 'shell' page instead. This is useful if your page is unable to be rendered on the server (because you use browser-only globals like `document` for example), but in most situations it's not recommended ([see appendix](glossary#SSR)).
+Normally, SvelteKit renders your page on the server before sending that HTML to the client where it's [hydrated](glossary#Hydration). This is also required for prerendering to save the full contents of a page.
+
+If you set `ssr` to `false`, it renders an empty 'shell' page instead. This is useful if your page is unable to be rendered on the server (because you use browser-only globals like `document` for example), but in most situations it's not recommended ([see appendix](glossary#SSR)).
 
 ```js
 /// file: +page.js
 export const ssr = false;
 // If both `ssr` and `csr` are `false`, nothing will be rendered!
 ```
 
-If you add `export const ssr = false` to your root `+layout.js`, your entire app will only be rendered on the client — which essentially means you turn your app into an SPA.
+If you add `export const ssr = false` to your root `+layout.js`, your entire app will only be rendered on the client — which essentially means you turn your app into an [SPA](glossary#SPA). You should not do this if your goal is to build a [statically generated site](glossary#SSG).
 
 > [!NOTE] If all your page options are boolean or string literal values, SvelteKit will evaluate them statically. If not, it will import your `+page.js` or `+layout.js` file on the server (both at build time, and at runtime if your app isn't fully static) so it can evaluate the options. In the second case, browser-only code must not run when the module is loaded. In practice, this means you should import browser-only code in your `+page.svelte` or `+layout.svelte` file instead.
 

documentation/docs/25-build-and-deploy/50-adapter-static.md

@@ -44,6 +44,8 @@ export const prerender = true;
 
 > [!NOTE] You must ensure SvelteKit's [`trailingSlash`](page-options#trailingSlash) option is set appropriately for your environment. If your host does not render `/a.html` upon receiving a request for `/a` then you will need to set `trailingSlash: 'always'` in your root layout to create `/a/index.html` instead.
 
+> [!NOTE] You must ensure SvelteKit's [`ssr`](page-options#ssr) option isn't set to `false`. Otherwise, prerendering will save an empty 'shell' page instead of the fully rendered content.
+
 ## Zero-config support
 
 Some platforms have zero-config support (more to come in future):

documentation/docs/60-appendix/60-glossary.md

@@ -36,12 +36,13 @@ Traditional applications that render each page view on the server — such as th
 
 Prerendering means computing the contents of a page at build time and saving the HTML for display. This approach has the same benefits as traditional server-rendered pages, but avoids recomputing the page for each visitor and so scales nearly for free as the number of visitors increases. The tradeoff is that the build process is more expensive and prerendered content can only be updated by building and deploying a new version of the application.
 
-Not all pages can be prerendered. The basic rule is this: for content to be prerenderable, any two users hitting it directly must get the same content from the server, and the page must not contain [actions](form-actions). Note that you can still prerender content that is loaded based on the page's parameters as long as all users will be seeing the same prerendered content.
+For content to be prerenderable, any two users hitting it directly must get the same content from the server, and the page must not contain [actions](form-actions). Note that you can still prerender content that is loaded based on the page's parameters as long as all users will be seeing the same prerendered content. Prerendering all of your pages is also known as [Static Site Generation](#SSG).
 
 Pre-rendered pages are not limited to static content. You can build personalized pages if user-specific data is fetched and rendered client-side. This is subject to the caveat that you will experience the downsides of not doing SSR for that content as discussed above.
 
 In SvelteKit, you can control prerendering with [the `prerender` page option](page-options#prerender) and [`prerender` config](configuration#prerender) in `svelte.config.js`.
 
+
 ## PWA
 
 A progressive web app (PWA) is an app that's built using web APIs and technologies, but functions like a mobile or desktop app. Sites served as [PWAs can be installed](https://web.dev/learn/pwa/installation), allowing you to add a shortcut to the application on your launcher, home screen, or start menu. Many PWAs will utilize [service workers](service-workers) to build offline capabilities.
@@ -62,7 +63,7 @@ In SvelteKit, you can [build SPAs with `adapter-static`](single-page-apps).
 
 Static Site Generation (SSG) is a term that refers to a site where every page is prerendered. One benefit of fully prerendering a site is that you do not need to maintain or pay for servers to perform SSR. Once generated, the site can be served from CDNs, leading to great “time to first byte” performance. This delivery model is often referred to as JAMstack.
 
-In SvelteKit, you can do static site generation by using [`adapter-static`](adapter-static) or by configuring every page to be prerendered using [the `prerender` page option](page-options#prerender) or [`prerender` config](configuration#prerender) in `svelte.config.js`.
+In SvelteKit, you can do static site generation by using [`adapter-static`](adapter-static) or by configuring every page to be [prerendered](#Prerendering) using [the `prerender` page option](page-options#prerender) or [`prerender` config](configuration#prerender) in `svelte.config.js`.
 
 ## SSR