The will-change property in CSS signals the browser that an element is about to change, allowing it to optimize rendering. 1. It informs the browser which properties will change, such as transform, opacity, scroll-position, or contents. 2. The browser may then promote the element to its own layer, pre-allocate resources, and avoid costly re-optimizations. 3. Use it selectively—before changes occur (e.g., on hover) and remove it afterward—to avoid unnecessary resource consumption. 4. Unlike older hacks like translateZ(0) or opacity: 0.99, will-change provides a more intentional and efficient way to prepare for visual changes without forcing layers unnecessarily.
The will-change
property in CSS is a hint to the browser that an element is expected to change, which can help improve performance by allowing the browser to optimize how it handles rendering and compositing before the actual changes happen.
What does will-change
actually do?
Browsers are pretty good at optimizing rendering on their own. However, sometimes they don’t know ahead of time what’s going to change — especially when those changes are triggered by user interaction or JavaScript. That’s where will-change
comes in.
By using will-change
, you're telling the browser: "Hey, I’m about to animate or modify this element in some way — get ready." In response, the browser might take steps like promoting the element to its own layer, pre-allocating resources, or avoiding certain optimizations that would be expensive to undo later.
Common values include:
will-change: transform;
will-change: opacity;
will-change: scroll-position;
will-change: contents;
Each tells the browser what kind of change is coming, so it can prepare accordingly.
When should you use will-change
?
It’s most useful when you know something will change soon — for example, during hover effects, transitions, or animations. A common use case might be:
.button:hover { will-change: transform; }
This helps the browser prepare for a transform-based animation (like a scale-up on hover) before it actually starts happening.
However, don’t overuse it. If you apply will-change
to too many elements or for properties that rarely change, you could end up hurting performance instead of helping it. Creating layers and prepping for changes uses memory and processing power, so it's best reserved for elements that genuinely benefit from the optimization.
Some general guidelines:
- Use it only when you notice jank or lag in animations.
- Apply it just before the change happens (e.g., on hover or focus), not too early.
- Remove it once the change is done if the element won’t be changing again soon.
How is it different from translateZ(0)
or opacity: 0.99
?
You may have seen people using tricks like transform: translateZ(0)
or opacity: 0.99
to force hardware acceleration. These work by triggering the creation of a new compositor layer, similar to what will-change
might do — but with a key difference: those hacks are blunt instruments.
They force layer creation regardless of whether it's needed, and can lead to excessive memory usage or slower rendering due to too many layers. will-change
, on the other hand, gives a more intentional signal to the browser, allowing it to make smarter decisions.
Still, both approaches are about preparing the browser for upcoming visual changes. The difference is that will-change
is designed specifically for this purpose and is more future-proof as browsers evolve.
Used wisely, will-change
can smooth out animations and interactions without much effort. But like any performance tool, it works best when applied selectively and thoughtfully.
The above is the detailed content of How does CSS will-change property help with performance?. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

There are three ways to create a CSS loading rotator: 1. Use the basic rotator of borders to achieve simple animation through HTML and CSS; 2. Use a custom rotator of multiple points to achieve the jump effect through different delay times; 3. Add a rotator in the button and switch classes through JavaScript to display the loading status. Each approach emphasizes the importance of design details such as color, size, accessibility and performance optimization to enhance the user experience.

To deal with CSS browser compatibility and prefix issues, you need to understand the differences in browser support and use vendor prefixes reasonably. 1. Understand common problems such as Flexbox and Grid support, position:sticky invalid, and animation performance is different; 2. Check CanIuse confirmation feature support status; 3. Correctly use -webkit-, -moz-, -ms-, -o- and other manufacturer prefixes; 4. It is recommended to use Autoprefixer to automatically add prefixes; 5. Install PostCSS and configure browserslist to specify the target browser; 6. Automatically handle compatibility during construction; 7. Modernizr detection features can be used for old projects; 8. No need to pursue consistency of all browsers,

Themaindifferencesbetweendisplay:inline,block,andinline-blockinHTML/CSSarelayoutbehavior,spaceusage,andstylingcontrol.1.Inlineelementsflowwithtext,don’tstartonnewlines,ignorewidth/height,andonlyapplyhorizontalpadding/margins—idealforinlinetextstyling

Setting the style of links you have visited can improve the user experience, especially in content-intensive websites to help users navigate better. 1. Use CSS's: visited pseudo-class to define the style of the visited link, such as color changes; 2. Note that the browser only allows modification of some attributes due to privacy restrictions; 3. The color selection should be coordinated with the overall style to avoid abruptness; 4. The mobile terminal may not display this effect, and it is recommended to combine it with other visual prompts such as icon auxiliary logos.

Use the clip-path attribute of CSS to crop elements into custom shapes, such as triangles, circular notches, polygons, etc., without relying on pictures or SVGs. Its advantages include: 1. Supports a variety of basic shapes such as circle, ellipse, polygon, etc.; 2. Responsive adjustment and adaptable to mobile terminals; 3. Easy to animation, and can be combined with hover or JavaScript to achieve dynamic effects; 4. It does not affect the layout flow, and only crops the display area. Common usages are such as circular clip-path:circle (50pxatcenter) and triangle clip-path:polygon (50%0%, 100 0%, 0 0%). Notice

To create responsive images using CSS, it can be mainly achieved through the following methods: 1. Use max-width:100% and height:auto to allow the image to adapt to the container width while maintaining the proportion; 2. Use HTML's srcset and sizes attributes to intelligently load the image sources adapted to different screens; 3. Use object-fit and object-position to control image cropping and focus display. Together, these methods ensure that the images are presented clearly and beautifully on different devices.

Different browsers have differences in CSS parsing, resulting in inconsistent display effects, mainly including the default style difference, box model calculation method, Flexbox and Grid layout support level, and inconsistent behavior of certain CSS attributes. 1. The default style processing is inconsistent. The solution is to use CSSReset or Normalize.css to unify the initial style; 2. The box model calculation method of the old version of IE is different. It is recommended to use box-sizing:border-box in a unified manner; 3. Flexbox and Grid perform differently in edge cases or in old versions. More tests and use Autoprefixer; 4. Some CSS attribute behaviors are inconsistent. CanIuse must be consulted and downgraded.

The choice of CSS units depends on design requirements and responsive requirements. 1.px is used for fixed size, suitable for precise control but lack of elasticity; 2.em is a relative unit, which is easily caused by the influence of the parent element, while rem is more stable based on the root element and is suitable for global scaling; 3.vw/vh is based on the viewport size, suitable for responsive design, but attention should be paid to the performance under extreme screens; 4. When choosing, it should be determined based on whether responsive adjustments, element hierarchy relationships and viewport dependence. Reasonable use can improve layout flexibility and maintenance.
