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Create a context once, provide its value above the components that need it, and read it with useContext at the top level of each function component. React gives each reader the value from the nearest matching provider above it in the component tree.
How to use Context: the basic pattern
Context makes information available to descendants without passing it through every intermediate component as props. The three steps are to create a context, place a provider above its readers, and call useContext where the value is needed.
- Create the context outside components. Import
createContextfrom React and declare the context at module scope. Use a meaningful default if one is appropriate; otherwise, usenull. - Provide a value above the readers. Render the context as a provider around the relevant part of the tree and pass the current value.
- Read the value in a function component. Import
useContextand call it at the top level of the component, passing the context object.
import { createContext, useContext, useState } from 'react';
const ThemeContext = createContext('light');
function App() {
const [theme, setTheme] = useState('dark');
return (
<ThemeContext value={theme}>
<Toolbar />
</ThemeContext>
);
}
function Toolbar() {
const theme = useContext(ThemeContext);
return <div className={theme}>Toolbar</div>;
}This example follows the current provider syntax in React’s createContext documentation. If you are working with a React version whose documentation uses <ThemeContext.Provider value={theme}>, use the syntax supported by that version. The useContext reference explains how consumers find their provider.
Where to create and place a context
Declare it at module scope
Call createContext outside component functions. If the provider and readers are in different files, export the context from a shared module and import the same context object in both places. Context matching is based on the context object, not merely on the variable’s name.
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Put the provider above every component that reads it
useContext(ThemeContext) searches upward through the React tree and uses the closest provider for that context. Intermediate components do not need to forward the value. A nested provider of the same context intentionally supplies a different value to its own descendants.
A component cannot read a provider that it returns itself: its own useContext call only sees providers above that component. If the reader needs a value, move the provider into an ancestor or split the provider and reader into separate components. React describes these rules in useContext.
Defaults and changing values
The value passed to createContext(defaultValue) is a static fallback. React uses it only when there is no matching provider above the consumer; it does not act as changing state. To supply dynamic data, render a provider with the current value.
A common approach is to keep the data in state in an ancestor and use that state as the provider value. When the value changes, components reading that context below the provider update. React compares the previous and next values with Object.is. Wrapping a reader in memo does not stop it from receiving a changed context value. See the useContext reference for the update behavior.
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Use props when they make a component’s dependencies clearer and the data only needs to travel a short distance. Consider composition with children if intermediate components merely relay information and do not use it themselves. Context is useful when data is needed by components at different depths across a subtree—for example, a theme, current account, routing information, or shared state. React’s guide, Passing Data Deeply with Context, explains this trade-off.
| Approach | Fits when | What to consider |
|---|---|---|
| Props | A parent passes data to direct children or through a manageable chain. | Dependencies are explicit at each component boundary, but intermediate components may need to relay values they do not use. |
| Children composition | Intermediate components only need to position or wrap a component that uses the data. | Can avoid threading a value through components that do not consume it. |
| Context | Multiple descendants across a subtree need the same information. | Readers depend on the context provider above them; nested providers can give separate subtrees distinct values. |
There is no universal performance ranking between props and context established by these API references. Choose based on the shape of the component tree and how clearly you want dependencies to be expressed.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Context values, objects, and rendering
Context values can be objects or functions as well as strings and other values. If a provider’s parent creates a fresh object or function on every render, its identity changes; that can cause context readers to render again even when the information inside is effectively unchanged.
Do not add memoization automatically. If that extra work matters in your component, React’s useContext guidance shows how to stabilize a function with useCallback and the containing value with useMemo. Treat these as targeted performance optimizations, not requirements for using Context.
Best Value
Using Context for reducer-managed shared state
When shared state has more involved update logic, React demonstrates pairing useReducer with two contexts: one for the current state and one for the dispatch function. A provider component owns the reducer state; descendants can read state and dispatch actions without repeatedly passing them through intermediate components. Follow the pattern in React’s Scaling Up with Reducer and Context guide.
TypeScript: make a missing provider visible
In TypeScript, the value passed to createContext determines the inferred context type. If there is no sensible fallback, initialize the context with null and expose a custom consumer hook that checks for a missing provider and throws an error. After the check, the hook can return a non-null value to its callers. React documents this approach in Using TypeScript.
How function components differ from class components
Function components read context with the useContext Hook. Class components use static contextType and then read the value through this.context; the class API supports one context at a time. React describes the class API as equivalent to useContext for function components in its Component reference.
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