The margin-trim property allows the container to trim the margins of its children where they adjoin the container’s edges.


Margins are not trimmed by the container.

For in-flow boxes contained by this box, block-axis margins adjacent to the box's edges are truncated to zero.

It also truncates any margins collapsed with such a margin.

Trims the margins of in-flow boxes and floats whose margins coincide with the container's content edge.

Formal definition

Initial valuenone
Applies toBlock containers and multi-column containers. It also applies to ::first-letter and ::first-line.
Computed valueas specified
Animation typediscrete

Formal syntax

none | in-flow | all


Basic usage

Once support is implemented for this property, it will probably work like so:

When you've got a container with some inline children and you want to put a margin between each child but not have it interfere with the spacing at the end of the row, you might do something like this:

article {
  background-color: red;
  margin: 20px;
  padding: 20px;
  display: inline-block;

article > span {
  background-color: black;
  color: white;
  text-align: center;
  padding: 10px;
  margin-right: 20px;

The problem here is that you'd end up with 20px too much spacing at the right of the row, so you'd maybe do this to fix it:

span:last-child {
  margin-right: 0;

It is a pain having to write another rule to achieve this, and it is also not very flexible. Instead, margin-trim could fix it:

 article {
  margin-trim: in-flow;


Specification Status
CSS Box Model Module Level 4
The definition of 'margin-trim' in that specification.
Editor's Draft

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Chrome No support NoEdge No support NoFirefox No support No
No support No
Notes See bug 1506241.
IE No support NoOpera No support NoSafari No support NoWebView Android No support NoChrome Android No support NoFirefox Android No support No
No support No
Notes See bug 1506241.
Opera Android No support NoSafari iOS No support NoSamsung Internet Android No support No


No support  
No support
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
See implementation notes.
See implementation notes.

See also