The margin-block-start CSS property defines the logical block start margin of an element, which maps to a physical margin depending on the element's writing mode, directionality, and text orientation.


/* <length> values */
margin-block-start: 10px;  /* An absolute length */
margin-block-start: 1em;   /* relative to the text size */
margin-block-start: 5%;    /* relative to the nearest block container's width */

/* Keyword values */
margin-block-start: auto;

/* Global values */
margin-block-start: inherit;
margin-block-start: initial;
margin-block-start: unset;

It corresponds to the margin-top, margin-right, margin-bottom, or margin-left property depending on the values defined for writing-mode, direction, and text-orientation.

It relates to margin-block-end, margin-inline-start, and margin-inline-end, which define the other margins of the element.


The margin-block-start property takes the same values as the margin-left property.

Formal definition

Initial value0
Applies tosame as margin
Percentagesdepends on layout model
Computed valueif specified as a length, the corresponding absolute length; if specified as a percentage, the specified value; otherwise, auto
Animation typea length

Formal syntax



Setting block start margin


  <p class="exampleText">Example text</p>


div {
  background-color: yellow;
  width: 120px;
  height: 120px;

.exampleText {
  writing-mode: vertical-lr;
  margin-block-start: 20px;
  background-color: #c8c800;



Browser compatibility

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See also