CSS inset-block-start Property

Last Updated : 10 Jun, 2026

The CSS inset-block-start property specifies the offset of a positioned element from the block-start edge of its containing block. It adapts automatically to different writing modes and text directions.

  • Sets the offset from the block-start edge.
  • Works with positioned elements.
  • Adapts to different writing modes and text directions.
  • Logical equivalent of the top property.

Syntax:

inset-block-start: auto | length | percentage | inherit | initial | unset;

Property Values

  • auto: Uses the browser's default positioning.
  • length: Sets a fixed offset value.
  • percentage: Sets the offset as a percentage of the containing block.
  • inherit: Inherits the value from the parent element.
  • initial: Sets the property to its default value (auto).
  • unset: Resets the property to its inherited or initial value.

Examples of inset-block-start property in CSS

Here are some examples:

Example 1: The inset-block-start: 0 property positions the green bar at the block-start edge (top) of the container.

HTML
<!--Driver Code Starts-->
<!DOCTYPE html>
<html>
<head>
    <title>CSS | inset-block-start Property</title>
<!--Driver Code Ends-->

    <style>
        body {
            background-color: #e6e6e6;
            text-align: center;
            font-family: "Times New Roman", serif;
        }

        h1 {
            color: green;
            font-size: 32px;
            margin-bottom: 10px;
        }

        h2 {
            font-size: 18px;
            margin-bottom: 35px;
        }

        .container {
            position: relative;
            width: 200px;
            height: 70px;
            margin: auto;
            background-color: turquoise;
        }

        .box {
            position: absolute;
            inset-block-start: 0;
            left: 0;
            width: 100%;
            height: 10px;
            background-color: green;
        }

        .text {
            padding-top: 10px;
            font-size: 18px;
        }
    </style>

<!--Driver Code Starts-->
</head>

<body>
    <h1>Geeksforgeeks</h1>
    <h2>CSS | inset-block-start Property</h2>

    <div class="container">
        <div class="box"></div>
        <div class="text">
            A Computer Science<br>
            Portal for Geeks
        </div>
    </div>

</body>
</html>
<!--Driver Code Ends-->

 Example 2: The inset-block-start: 0 property positions the cyan box at the block-start edge of the green container.

HTML
<!--Driver Code Starts-->
<!DOCTYPE html>
<html>
<head>
    <title>CSS | inset-block-start Property</title>
<!--Driver Code Ends-->

    <style>
        body {
            background: #e6e6e6;
            text-align: center;
            font-family: "Times New Roman", serif;
        }

        h1 {
            color: green;
            font-size: 32px;
            margin-bottom: 15px;
        }

        .container {
            position: relative;
            width: 190px;
            height: 95px;
            margin: auto;
            background: green;
        }

        .box {
            position: absolute;
            inset-block-start: 0;
            inset-inline-start: 0;

            width: 50px;
            height: 95px;

            background: cyan;
            writing-mode: vertical-rl;
            text-align: center;
            font-size: 16px;
            line-height: 1.1;
        }
    </style>

<!--Driver Code Starts-->
</head>

<body>

    <h1>Geeksforgeeks</h1>

    <h2>CSS | inset-block-start Property</h2>

    <div class="container">
        <div class="box">
            A Computer Science Portal for Geeks
        </div>
    </div>

</body>
</html>
<!--Driver Code Ends-->
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