Why is React DevTools needed?

#What is React DevTools

React DevTools is a browser extension (Chrome, Firefox, Edge, and so on) that lets you view, explore, and debug the tree of React components right inside the developer tools (DevTools).

In essence, it is "an interactive window into the Virtual DOM".

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#Why it is needed

React DevTools helps you:

1. Study the component structure

• see the React component tree;
• see which components are nested inside each other;
• understand how the UI is built.

2. Track props and state

• you can click any component and see its current state;
• you can change state and props right inside DevTools - React will update the UI immediately;
• convenient for testing and finding bugs.

3. Profile performance

• the Profiler tab shows which components re-render and why;
• you can see "render time" and spot "heavy" areas;
• it helps optimize React.memo, useMemo, useCallback.

4. Track re-render cycles

• you can see which components update when state changes;
• you can understand where unnecessary renders happen.

5. Work with Context

• shows which components are subscribed to a context;
• shows when the context changes and who receives it.

6. Supports different versions of React

• works with both React DOM and React Native (via the standalone version);
• can show hooks (useState, useEffect, useRef, useContext, and so on).

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#What it looks like

After installation:

• a new "Components" tab appears in DevTools
• a tree of all React components;
• and a "Profiler" tab
• a tool for measuring performance.

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#Example of the Components tab

You can:

• select any component;

• see its:

  javascript

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  props: { name: "Alex", age: 25 } state: { isActive: true } hooks: [useState, useEffect, useRef...]

• change a value right from the interface -> the UI updates instantly.

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#Example of the Profiler tab

Lets you "record" a single render:

• click Start profiling;
• perform an action in the UI (for example, a click);
• click Stop profiling;
• see visually which components re-rendered, how long the update took, and which updates were "expensive".

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#How to install it

#Option 1: from the Chrome Web Store

React Developer Tools - Chrome Web Store

After installing -> open DevTools -> a Components tab appears.

#Option 2: npm version (for React Native or Electron)

A separate window opens that connects to the React app.

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#Why this matters

Without DevTools:

• it is inconvenient to see what data is actually passed into a component;
• it is hard to find the cause of an unnecessary render;
• it is difficult to understand how Context and Hooks work.

With DevTools: it is easy to diagnose bugs it is simple to optimize rendering you understand someone else's code faster

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#Summary

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Summary definition:

React DevTools is the official React developer tool that lets you explore, debug, and optimize React components and their performance.