January 15, 2024 - Let's dive straight into it and see what this hooks are really all about, their difference(s) and when to use them. useEffect allows you perform side effects from a function component.

December 1, 2020 - useLayoutEffect: If you need to mutate the DOM and/or do need to perform measurements · useEffect: If you don't need to interact with the DOM at all or your DOM changes are unobservable (seriously, most of the time you should use this).

Notice that even though the Tooltip component has to render in two passes (first, with tooltipHeight initialized to 0 and then with the real measured height), you only see the final result. This is why you need useLayoutEffect instead of useEffect for this example.

April 10, 2023 - So, with their identical syntaxes, what is the difference between these two hooks? Well, there are three key differences: The asynchronous nature of useEffect The DOM flashes The fact that useLayoutEffect is executed before useEffect.

Essentially, useLayoutEffect is a version of useEffect that fires before the browser repaints the screen, making it ideal for cases where you need to measure or manipulate the DOM and ensure changes are made before the browser renders the next frame.

February 15, 2020 - Thus you can manipulate what the user actually sees before the initial render. useEffect on the other hand always occurs AFTER the dom gets painted, thus you can’t use it to calculate something based on the dom (like current width of an auto-width ...

June 18, 2024 - The primary difference between useEffect and useLayoutEffect is when the callback is executed. With useEffect, the callback is executed asynchronously after the component has rendered and the screen has been updated. useLayoutEffect, on the ...

July 23, 2025 - Example: We use useLayoutEffect to add an effect that runs synchronously after each render of the component. Inside this effect, we update the count state by incrementing it by 1 whenever the count state itself changes.

June 4, 2024 - Essentially, useEffect lets you ... more flexible and efficient. The useLayoutEffect Hook is a variation of the useEffect Hook that runs synchronously before the browser repaints the screen....

September 5, 2021 - It does not block the browser from updating the UI. By default, it runs after every render, but dependencies can control its execution. ... useLayoutEffect is a React hook similar to useEffect, but it differs in timing.

March 13, 2023 - Use cases: useEffect is used for handling side effects that don't require synchronous updates, such as fetching data from an API, setting up event listeners, or updating the component's state. useLayoutEffect is used for side effects that require ...

July 15, 2020 - Notice how the version with useLayoutEffect only updates visually once even though the component rendered twice. The useEffect version, on the other hand, visually renders twice, so you see a flicker where the value is briefly 0.

January 31, 2026 - When to Use useLayoutEffect Over useEffect in React In React, useEffect is the primary way of handling side effects in function components. However, there’s another hook that often gets overlooked …

July 3, 2023 - The gif below shows two chat boxes — after the page loads, messages are “fetched” and then each chat box scrolls to the bottom. The left box uses the useLayoutEffect hook to scroll to the bottom and the right one uses useEffect. You can notice some strange flashing only in the right box using useEffect.

August 12, 2024 - As stated above the useEffect hook is asynchronous this has a significant drawback in that it can only be called after the component has been mounted. This implies that side effects that depend on the layout of the component cannot be carried out using useEffect. Now how do we solve this problem, this is where useLayoutEffect comes in.

November 5, 2024 - Unlike useEffect, which is asynchronous, useLayoutEffect executes synchronously. It waits until all DOM updates within it are completed, blocking the paint process until everything is applied.

September 25, 2023 - You wouldn’t want the user to ... zero for the start of the animation. useEffect would display that flash, whereas useLayoutEffect would let you inspect the height of the rendered div and then adjust it before the user got to see it....

August 5, 2024 - In contrast, useLayoutEffect is used for effects that must be deterministic and synchronous, such as preventing visual flicker or ensuring the correct reading of layout measurements.

March 23, 2022 - In useEffect, when a user triggers ... runs asynchronously in the background. ... In useLayoutEffect, the callback function runs synchronously before the screen is updated....