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In React, a controlled component gets its important value from props, while an uncontrolled component keeps that value locally. For native form fields, that distinction is concrete: value or checked controls the current value; defaultValue or defaultChecked sets only the initial value. Use controlled fields when React needs to coordinate or react to edits, and uncontrolled fields when you can leave the value in the DOM until you need it.
What is the difference between controlled and uncontrolled components in React?
These are useful design terms, not rigid categories that every component must fit. In React’s terminology, a controlled component has important information driven by props; an uncontrolled component keeps important information in its own local state. A controlled child lets its parent specify its behavior. An uncontrolled child needs less configuration from the parent, but is harder to coordinate with other components. Many components mix parent-provided props with their own local state. See React’s guide to sharing state between components.
| Question | Controlled | Uncontrolled |
|---|---|---|
| Where does the current value live? | In React state and is passed in through props. | In the form field’s current DOM value. |
| How does React learn about edits? | An event handler updates the backing state as the user edits. | The field changes its own DOM value; React need not process each edit. |
| How much parent configuration is needed? | The parent supplies the value and an update handler. | Usually less configuration; the parent can read the value when needed. |
| How do you read the value on submit? | Read the value from React state. | Read a named field using FormData. |
| What are the main constraints? | Update state synchronously and keep the value’s type stable. | Do not assume a later defaultValue change will replace the current value. |
How do value and defaultValue work?
For React’s native form controls, the prop names determine whether React controls the current value or only provides an initial one. These rules are specific to native fields; they are a practical example of the broader component-design distinction.
Text inputs
Use value to control a text input, and defaultValue to set its starting text without controlling later edits. A controlled input needs an onChange handler that synchronously updates the state supplying value. React’s <input> reference documents these rules.
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const [name, setName] = useState('');
<input
value={name}
onChange={event => setName(event.target.value)}
/>An uncontrolled field with initial text can be written as:
<input name="name" defaultValue="Taylor" />If a controlled input rerenders with its previous value because the handler did not update state synchronously, typing appears to revert.
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Checkboxes and radio buttons
Use checked to control whether a checkbox or radio button is selected, and defaultChecked to set its initial selection. For a controlled checkbox, keep the prop boolean and synchronously update it in the change handler. The value prop is not a substitute for controlling whether the field is checked.
Select menus
Use value on the parent <select> to control the selected option, or defaultValue to specify the initial selection. For a multiple-select field, either prop can receive an array of strings. Set selection on the <select>, not with a selected prop on an individual <option>. See React’s <select> reference.
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Textareas
A controlled <textarea> uses value and a synchronous update handler; an uncontrolled one can use defaultValue for its initial text. React’s <textarea> reference describes the same controlled-versus-initial-value distinction.
When should I use controlled or uncontrolled components?
Choose controlled state when other UI depends on each edit
Keep a field controlled when React needs to respond as the user types, when a parent coordinates related components, or when more than one action can change the same value. Examples include showing a live preview, mirroring text in another field, displaying validation while typing, or letting a button change the field. The parent can own the value and pass it, along with an update handler, to the child.
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Choose uncontrolled state when the DOM can hold the value until needed
An uncontrolled field is a reasonable fit when the parent does not need to coordinate every edit and only needs the value at a particular point, such as form submission. Give the field a name, then read it from the submitted form:
function handleSubmit(event) {
event.preventDefault();
const formData = new FormData(event.currentTarget);
const name = formData.get('name');
}
<form onSubmit={handleSubmit}>
<input name="name" defaultValue="Taylor" />
<button type="submit">Submit</button>
</form>React’s <form> reference also documents that successful function form actions reset uncontrolled fields.
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How do I keep two React inputs in sync?
Put their shared value in the closest common parent and pass it down to both inputs with handlers that update that shared state. React calls this lifting state up: there is one source of truth for the value, rather than separate copies in each child that can drift apart.
function NameFields() {
const [name, setName] = useState('');
return (
<>
<input value={name} onChange={event => setName(event.target.value)} />
<input value={name} onChange={event => setName(event.target.value)} />
</>
);
}Each input receives the same current value, and either input’s handler updates the state that both render from.
How do you avoid switching a field between controlled and uncontrolled?
A native field should not switch modes during its lifetime. For example, a text field that first renders with value={undefined} and later receives a string changes from uncontrolled to controlled. Initialize controlled text state to an empty string or normalize nullable data so that value is always a string. For a controlled checkbox, provide a boolean checked value. Keep the selected mode and value type consistent across renders.
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