What is the difference between full hydration and partial hydration?

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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 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) 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”

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

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What is the difference between full hydration and partial hydration?

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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