performance - CSS3 Transitions: Is "transition: all" slower than "transition: x"?

Question

I have a question about rendering speed for the css3 transition property.

Suppose I have a number of elements:

div, span, a {transition: all}

div {margin: 2px}
span {opacity: .5}
a:hover {background-position: left top}

div:hover {margin: -100px}
span:hover {opacity: 1}
a:hover {background-position: -5px top}

It's much more efficient to target all of the transitions for all of those elements using one declaration div, span, a {transition: all}. But my question is: would it be "faster" in terms of the smoothness and quickness of the animation rendering to target each element's specific transition property? For example:

div {margin: 2px; transition: margin .2s ease-in}
span {opacity: .5; transition: opacity .2s ease-in}
a {background-position: left top; transition: background .2s ease-in}

div:hover {margin: -100px}
span:hover {opacity: 1}
a:hover {background-position: -5px top}

My logic in asking this is that if the css "engine" has to search for "all" transition properties even if there is just one single property for an element, that it might slow things down.

Does anyone know if that's the case? Thanks!

Answer 1

Yes, using transition: all could cause major drawbacks in performance. There can be a lot of cases where the browser would look if it needs to make a transition, even if user won't see it, like the color changes, dimension changes etc.

The simplest example I can think of is this: http://dabblet.com/gist/1657661 — try to change the zoom level or the font's size and you'll see that everything become animated.Of course there couldn't be a lot of such user interactions, but there could be some interface changes that can cause the reflow and repaints in some blocks, that could tell the browser to try and animate those changes.

So, in general, it's recommended that you won't use the transition: all and would use the direct transitions instead.

There are some other things that can go wrong with the all transitions, like the splash of animation on page load, where it would at first render the initial styles for blocks and then apply the style with an animation. In a lot of cases it wouldn't be the thing that you want :)