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CSS mask-position Precise Mask Image Control

The CSS mask-position property allows precise control over mask image positioning.

Use keywords like 'top', 'bottom', 'left', 'right', 'center' or numerical values like percentages or lengths.

Enhance your web designs with flexible and dynamic positioning.

Introduction

The mask-position CSS property allows you to control where mask images are placed. It’s a great tool for web developers, introduced in December 2023, and works well with modern devices and browsers.

With mask-position, you can align masks to specific edges or use percentages for more dynamic positioning. This property helps you create unique designs by controlling mask images easily.

Specification

The mask-position property is part of the CSS Masking Module Level 1. This module helps you create complex visual effects by defining how mask images interact with elements on a web page.

You can find the specification for mask-position in the CSS Masking Module Level 1. Understanding this specification is important for using masking effectively in your projects.

Syntax

The mask-position property uses various values for flexible control over mask image positioning. Here’s the basic syntax:

mask-position: <position>;

Keyword Values

You can use predefined keywords:

mask-position: top;
mask-position: bottom;
mask-position: left;
mask-position: right;
mask-position: center;

Numerical Values

You can also use numerical values:

mask-position: 25% 75%;
mask-position: 0px 0px;
mask-position: 10% 8em;

Multiple Values

To apply multiple positions, separate them with commas:

mask-position: top right;
mask-position: 1rem 1rem, center;

Global Values

Global values provide additional control:

mask-position: inherit;
mask-position: initial;
mask-position: revert;
mask-position: revert-layer;
mask-position: unset;

Values

The mask-position property supports various values to specify the position of mask images.

`<position>`

The <position> value represents a 2D position. It can be keywords or numerical values.

Keywords: top, bottom, left, right, center
Numerical Values: Percentages (25%, 75%) or lengths (0px, 10em)

Multiple Values

You can specify multiple positions by separating them with commas:

mask-position: top right;
mask-position: 1rem 1rem, center;

Global Values

Global values include:

inherit: Inherits from the parent element.
initial: Sets the property to its initial value (0% 0%).
revert: Reverts to the user agent’s default.
revert-layer: Reverts to the value for that layer.
unset: Resets the property to its natural value.

mask-position: inherit;
mask-position: initial;
mask-position: revert;
mask-position: revert-layer;
mask-position: unset;

Formal Definition

The mask-position property is formally defined by its initial value, applicable elements, inheritance behavior, and how percentages and computed values are handled.

Initial Value

The initial value is 0% 0%, positioning the mask image at the top-left corner.

Applies To

Applies to all elements, except <defs> in SVG.

Inherited

Not inherited.

Percentages

Percentages refer to the mask painting area minus the mask layer image size.

Computed Value

Consists of two keywords and two offsets, given as absolute lengths or percentages.

Animation Type

The animation type is a repeatable list.

Formal Syntax

mask-position = <position>[#]

<position> =
  [left | center | right | top | bottom | <length-percentage>]
  [left | center | right] && [top | center | bottom]
  [left | center | right | <length-percentage>] [top | center | bottom | <length-percentage>]
  [left | right] [top | bottom] <length-percentage>

<length-percentage> = <length> | <percentage>

Examples

Using Keyword Values

<!DOCTYPE html>
<html>
<head>
  <style>
    .container {
      border: 3px solid black;
      background-color: rgb(136, 255, 0);
      width: 30%;
      height: 30vh;
    }
    .masked-element {
      width: 30%;
      height: 200px;
      background: green;
      border: 10px solid red;
      -webkit-mask-image: url("image.svg");
      -webkit-mask-repeat: no-repeat;
      mask-position: top;
    }
  </style>
</head>
<body>
  <div class="container">
    <div class="masked-element"></div>
  </div>
</body>
</html>

Using Numerical Values

<!DOCTYPE html>
<html>
<head>
  <style>
    .container {
      border: 3px solid black;
      background-color: rgb(136, 255, 0);
      width: 30%;
      height: 30vh;
    }
    .masked-element {
      width: 30%;
      height: 200px;
      background: green;
      border: 10px solid red;
      -webkit-mask-image: url("image.svg");
      -webkit-mask-repeat: no-repeat;
      mask-position: 0.2rem 30%;
    }
  </style>
</head>
<body>
  <div class="container">
    <div class="masked-element"></div>
  </div>
</body>
</html>

Using Multiple Values

<!DOCTYPE html>
<html>
<head>
  <style>
    .container {
      border: 3px solid black;
      background-color: rgb(136, 255, 0);
      width: 30%;
      height: 30vh;
    }
    .masked-element {
      width: 30%;
      height: 200px;
      background: green;
      border: 10px solid red;
      -webkit-mask-image: url("image1.svg"), url("image2.svg");
      -webkit-mask-repeat: no-repeat, no-repeat;
      mask-position: top right, 1rem 1rem;
    }
  </style>
</head>
<body>
  <div class="container">
    <div class="masked-element"></div>
  </div>
</body>
</html>

Browser Compatibility

The mask-position property is widely supported across modern browsers:

Chrome: Supported from version 1.
Safari: Supported from version 15.4.
Edge: Supported from version 79.
Firefox: Supported from version 53.
Opera: Supported from version 15.
Internet Explorer: Not supported.

Test your pages in multiple browsers and devices to ensure compatibility. Use feature detection techniques to provide fallback solutions for unsupported browsers.

Clipping and Masking in CSS: Learn more about clipping and masking techniques. Check out this comprehensive guide on CSS-Tricks.
CSS Masking Module Level 1: Dive deeper into the CSS Masking Module Level 1 specification. You can find the specification here.
MDN Web Docs: Explore the MDN Web Docs for more information on the mask-position property and other CSS properties.