To optimize CSS animation performance, you must first select appropriate attributes and reduce rearrangement and redrawing; 1. Use will-change and translateZ to inform the browser element in advance that changes will be made, but avoid abuse; 2. Use transform and opacity animations first because they do not trigger reordering; 3. Control the frame rate to maintain 60fps, avoid forced synchronous layout, and use requestAnimationFrame to arrange logic; 4. Use hardware acceleration reasonably and only turn on when necessary to avoid layer explosions affecting GPU performance.

CSS animations can make web pages more vivid, but if used improperly, it may slow down page performance and even make user experience worse. If you want the animation to be smooth without affecting performance, the key is to select the right attributes, control the rendering rhythm, and minimize rearrangement and redrawing.

Use will-change and translateZ well

These two properties are often used to "tell" the browser that an element is about to change, so that it can be prepared in advance. For example, if you want to move an element, you can add transform: translateZ(0) or will-change: transform , so that the browser may promote it to an independent layer, and render it through GPU, and the animation will be smoother.

But don't abuse it! If you add these attributes to too many elements, it will lead to excessive memory usage and even affect synthesis efficiency. It's best to use it only on elements that really need animation and remove it after the animation is over (especially will-change ).

Try to only move the transform and opacity properties

Not all CSS properties are as lightweight when animations. When properties such as width , height , top , and left change, they often trigger rearrangement or redraw, which is relatively expensive. transform and opacity almost never trigger reordering because they belong to the synthesis stage and are more suitable for animation.

For example:

 /* recommend*/
transition: transform 0.3s ease;

/* Not very recommended*/
transition: width 0.3s ease;

So if you can use transform: translateY() to move, don’t use top ; if you can use opacity to control transparency, don’t use visibility .

Control frame rates and avoid forced synchronous layouts

Ideally, the animation should be kept at 60fps (60 frames per second), which means that each frame will take about 16ms to complete. If too much calculation or DOM operation is done during the animation execution, frames may be dropped.

One of the common problems is "forced synchronization layout". For example, if you read the dimensions of an element in JS and then immediately modify its style, it will cause the browser to complete the reorder before continuing, which will jamm the animation process.

Solutions include:

• Avoid frequent reading and writing layout information in animation frames
• Use requestAnimationFrame to arrange animation logic
• Put complex calculations into Web Worker (if applicable)

Use hardware acceleration appropriately but not overly depend on it

Many people think that as long as the hardware acceleration animation is turned on, it will definitely be fast, but in fact it is not. Hardware acceleration does improve the performance of some animations, but it is not a panacea. Overuse may cause the layer to explode, which will increase the burden on the GPU.

The recommended approach is:

• Only turn on when necessary (such as complex animations, scrolling parallax, etc.)
• Don't add translateZ(0) to each element
• Test performance under different devices, especially low-end devices

Basically that's it. Optimizing CSS animation is not difficult. The key is to understand which attributes are expensive and how to use the browser mechanism to reduce the burden. If done well, the animation will not only look good, but it will not slow down the page.

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