useDebugValue Hook

🪝 Introduction to useDebugValue

The useDebugValue Hook is a React Hook that lets you display custom debugging information for your own custom Hooks in React Developer Tools. It does not affect the user interface or application behavior, but it helps developers understand the internal state of custom Hooks while debugging.

Important

useDebugValue is intended for custom Hook authors. Most React applications do not need to use it directly.

🎯 Why Use useDebugValue?

When building reusable custom Hooks, it can be difficult to understand their current state while debugging. useDebugValue allows you to provide meaningful labels that appear in React Developer Tools, making custom Hooks easier to inspect and debug.

  • Display custom information in React Developer Tools.
  • Improve debugging of custom Hooks.
  • Make reusable Hooks easier to understand.
  • Provide descriptive debugging labels.

⚙️ Syntax

Basic Syntax

useDebugValue(value);

useDebugValue(value, format);
ParameterDescription
valueThe value displayed in React Developer Tools.
formatAn optional formatting function that transforms the displayed value.

🔄 How useDebugValue Works

Custom Hook Executes
Call useDebugValue()
React Stores the Debug Value
React Developer Tools Displays the Value
Developers Inspect the Hook

💻 Example 1: Basic Usage

Simple Debug Value

import { useDebugValue, useState } from "react";

function useCounter() {
  const [count, setCount] = useState(0);

  useDebugValue(count);

  return {
    count,
    increment: () => setCount(c => c + 1)
  };
}

When inspecting the custom Hook in React Developer Tools, the current counter value is displayed as debug information.

💻 Example 2: Formatting the Debug Value

Formatted Debug Value

import { useDebugValue } from "react";

function useOnlineStatus(isOnline) {
  useDebugValue(
    isOnline,
    status => status ? "Online" : "Offline"
  );

  return isOnline;
}

The formatting function converts the raw value into a more readable label that appears in React Developer Tools.

💻 Example 3: Custom Hook with Status

Displaying Hook State

import {
  useDebugValue,
  useState
} from "react";

function useLoading() {
  const [loading] = useState(false);

  useDebugValue(
    loading,
    value => value ? "Loading" : "Ready"
  );

  return loading;
}

Instead of displaying true or false, React Developer Tools displays descriptive text that is easier to understand.

📊 Without vs With useDebugValue

Without useDebugValueWith useDebugValue
Limited debugging information.Custom Hook values appear in React Developer Tools.
Harder to inspect custom Hooks.Hook state is easier to understand.
No descriptive labels.Meaningful debug information is displayed.

📅 Debugging Lifecycle

🎯 Common Use Cases

Display the internal state of reusable custom Hooks.

Show descriptive labels such as "Loading", "Connected", or "Offline".

Format complex values into developer-friendly output.

Improve debugging support in shared Hook libraries.

⚠️ Common Mistakes

  • Using useDebugValue in ordinary components instead of custom Hooks.
  • Expecting debug values to appear in the application UI.
  • Adding unnecessary debug values to every Hook.
  • Displaying overly complex or difficult-to-read information.

Warning

useDebugValue is intended only for debugging. It has no effect on the rendered user interface.

📊 useDebugValue vs console.log()

FeatureuseDebugValueconsole.log()
PurposeDisplay Hook information in React Developer Tools.Print messages in the browser console.
Visible ToReact Developer Tools users.Anyone viewing the browser console.
Typical UsageCustom Hook debugging.General debugging and logging.
Affects UI❌ No.❌ No.

✅ Best Practices

  • Use useDebugValue only inside custom Hooks.
  • Provide short, meaningful debug labels.
  • Use the formatting function for complex values.
  • Avoid adding debug values to every Hook unless they improve debugging.
  • Remember that this Hook is a developer tool, not a user-facing feature.

📚 Official Resource

Learn more about useDebugValue in the official React documentation at React useDebugValue Documentation.

Summary

The useDebugValue Hook helps developers inspect custom Hooks by displaying meaningful debug information in React Developer Tools. It is primarily intended for reusable Hook libraries and advanced debugging scenarios, making custom Hooks easier to understand, maintain, and debug without affecting application behavior.