Streaming SSR

Analog supports progressive streaming server-side rendering, flushing the response to the browser as the app renders instead of buffering the whole document until it is complete.

The document head is sent immediately, each @defer (hydrate …) block is sent the moment it resolves on the server, and the authoritative document arrives last — so a slow block never holds back the rest of the page.

Experimental

Streaming SSR is experimental and opt-in. It requires Angular 21 or later and builds on incremental hydration. The default buffered Server Side Rendering path is unchanged.

Enabling streaming

Enable the experimental.streaming option in your Vite config:

// vite.config.ts
import analog from '@analogjs/platform';
import { defineConfig } from 'vite';

export default defineConfig({
  plugins: [analog({ experimental: { streaming: true } })],
});

Then use renderStream instead of render in main.server.ts:

// src/main.server.ts
import { renderStream } from '@analogjs/router/server';
import { config } from './app/app.config.server';
import { AppComponent } from './app/app.component';

export default renderStream(AppComponent, config);

Streaming builds on incremental hydration, so enable it in your client providers. On Angular 21 use withIncrementalHydration(); on Angular 22+ it is enabled by default with provideClientHydration():

// src/app/app.config.ts
import {
  provideClientHydration,
  withIncrementalHydration,
} from '@angular/platform-browser';

export const appConfig: ApplicationConfig = {
  providers: [
    provideClientHydration(withIncrementalHydration()),
    // ...
  ],
};

Streaming deferred blocks

Content that should stream progressively goes in a @defer block with a hydrate trigger. Each block is rendered eagerly on the server, streamed as it resolves, and hydrated on the client when its trigger fires:

<h1>Dashboard</h1>

@defer (hydrate on immediate) {
  <app-activity-feed />
} @placeholder {
  <p>Loading activity…</p>
}

@defer (hydrate on viewport) {
  <app-recommendations />
} @placeholder {
  <p>Loading recommendations…</p>
}

A block backed by asynchronous data (for example an httpResource) keeps the render pending until its data resolves, so the block streams with its final content and the page's time-to-first-byte is unaffected.

Title and meta

Because the document head is flushed before the app renders, a title or meta set during render (via the Title/Meta services or route metadata) is applied to the streamed document once the render completes, before hydration runs. Search engine crawlers are served a buffered render with a fully resolved head instead of the streamed shell.

Opting a route out of streaming

Disable streaming for specific routes with a streaming: false route rule, the same way ssr: false disables SSR. Matching routes fall back to a buffered render (no streaming, but SSR and hydration still work):

// vite.config.ts
import analog from '@analogjs/platform';
import { defineConfig } from 'vite';

export default defineConfig({
  plugins: [
    analog({
      experimental: { streaming: true },
      nitro: {
        routeRules: {
          '/report': { streaming: false },
        },
      },
    }),
  ],
});