What is the difference between full hydration and partial hydration?

Question

ICSM · Answer

In 
Angular, full hydration and partial hydration are related to
hydration after
Server-Side Rendering (SSR)—how much of the server-rendered HTML Angular reuses on the client instead of re-rendering it.
1. Full Hydration (Angular)
Full hydration means:
Angular reuses the entire SSR-generated DOMAll components, bindings, events, and directives are fully connected on the clientNo DOM is destroyed and recreated
What happens
Server renders HTML (Angular Universal / 
SSR)Browser loads the pageAngular attaches event listeners and change detection to the existing DOMApp becomes interactive without re-rendering
Benefits
Faster Time to Interactive (TTI)No layout shift or flickerBetter SEO + performanceLower CPU and memory usage
Angular example
bootstrapApplication(AppComponent, {
  providers: [
    provideClientHydration()
  ]
});
This enables full hydration.
2. Partial Hydration (Angular)
Partial hydration means:
Only some components are hydrated on the clientOther parts stay static HTMLAngular hydrates components on demand
What happens
Server renders the full page
Client hydrates only:
visible componentsinteractive componentscomponents triggered by user action
Use cases
Large pagesContent-heavy apps (blogs,
news sites)Above-the-fold interactivity first
Example idea (conceptual)
andlt;app-comments ngSkipHydrationandgt;andlt;/app-commentsandgt;
@Component({
  selector: 'app-comments',
  host: { ngSkipHydration: '' }
})
export class CommentsComponent {}
This component is excluded from initial hydration and can be hydrated later.
3. Key differences (Angular-specific)
Aspect
Full Hydration
Partial Hydration
DOM reuse
Entire DOM
Selected components
Interactivity
Immediate everywhere
Gradual / on-demand
Performance
Good
Better for large apps
Complexity
Simple
More complex
Control
Global
Per-component
4. When to use what?
Use Full Hydration when:
App is medium-sizedMost components are interactiveYou want simplest SSR setup
Use Partial Hydration when:
App is large or content-heavyOnly parts need interactivityPerformance is critical
5. Angular versions note
Angular 16+: Hydration introducedAngular 17+: Improved hydration stabilityAngular 18–21: Better support for fine-grained / partial hydration patterns
Simple analogy
Full hydration → “Wake up the whole app at once”Partial hydration → “Wake up only what the user touches”
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What is the difference between full hydration and partial hydration?

ICSM

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1 Answers

1. Full Hydration (Angular)

What happens

Benefits

Angular example

2. Partial Hydration (Angular)

What happens

Use cases

Example idea (conceptual)

3. Key differences (Angular-specific)

4. When to use what?

Use Full Hydration when:

Use Partial Hydration when:

5. Angular versions note

Simple analogy

Liked By

Aspect	Full Hydration	Partial Hydration
DOM reuse	Entire DOM	Selected components
Interactivity	Immediate everywhere	Gradual / on-demand
Performance	Good	Better for large apps
Complexity	Simple	More complex
Control	Global	Per-component