leptos/examples/ssr_modes/README.md

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# SSR Modes Example
This example shows the different "rendering modes" that can be used while server-side rendering an application.
## Getting Started
See the [Examples README](../README.md) for setup and run instructions.
## Server-Side Rendering Modes
1. **Synchronous**: Serve an HTML shell that includes `fallback` for any `Suspense`. Load data on the client, replacing `fallback` once they're loaded.
- *Pros*: App shell appears very quickly: great TTFB (time to first byte).
- *Cons*: Resources load relatively slowly; you need to wait for JS + Wasm to load before even making a request.
2. **Out-of-order streaming**: Serve an HTML shell that includes `fallback` for any `Suspense`. Load data on the **server**, streaming it down to the client as it resolves, and streaming down HTML for `Suspense` nodes.
- *Pros*: Combines the best of **synchronous** and **`async`**, with a very fast shell and resources that begin loading on the server.
- *Cons*: Requires JS for suspended fragments to appear in correct order. Weaker meta tag support when it depends on data that's under suspense (has already streamed down `<head>`)
3. **In-order streaming**: Walk through the tree, returning HTML synchronously as in synchronous rendering and out-of-order streaming until you hit a `Suspense`. At that point, wait for all its data to load, then render it, then the rest of the tree.
- *Pros*: Does not require JS for HTML to appear in correct order.
- *Cons*: Loads the shell more slowly than out-of-order streaming or synchronous rendering because it needs to pause at every `Suspense`. Cannot begin hydration until the entire page has loaded, so earlier pieces
of the page will not be interactive until the suspended chunks have loaded.
4. **`async`**: Load all resources on the server. Wait until all data are loaded, and render HTML in one sweep.
- *Pros*: Better handling for meta tags (because you know async data even before you render the `<head>`). Faster complete load than **synchronous** because async resources begin loading on server.
- *Cons*: Slower load time/TTFB: you need to wait for all async resources to load before displaying anything on the client.