preserveAspectRatio

The preserveAspectRatio attribute indicates how an element with a viewBox providing a given aspect ratio must fit into a viewport with a different aspect ratio.

The aspect ratio of an SVG image is defined by the viewBox attribute. Therefore, if viewBox isn't set, the preserveAspectRatio attribute has no effect on SVG's scaling (except in the case of the <image> element, where preserveAspectRatio behaves differently as described below).

Syntax

preserveAspectRatio="<align> [<meet or slice>]"

The preserveAspectRatio attribute value consists of up to two keywords: a required alignment value and an optional meet or slice keyword.

The alignment value indicates whether to force uniform scaling and, if so, the alignment method to use in case the aspect ratio of the viewBox doesn't match the aspect ratio of the viewport. xMidYMid is the default value. The alignment value must be one of the following keyword values:

none: Does not force uniform scaling. Scale the graphic content of the given element non-uniformly if necessary such that the element's bounding box exactly matches the viewport rectangle. Note that if <align> is none, then the optional <meetOrSlice> value is ignored.
xMinYMin: Forces uniform scaling. Align the <min-x> of the element's viewBox with the smallest X value of the viewport. Align the <min-y> of the element's viewBox with the smallest Y value of the viewport.
xMidYMin: Forces uniform scaling. Align the midpoint X value of the element's viewBox with the midpoint X value of the viewport. Align the <min-y> of the element's viewBox with the smallest Y value of the viewport.
xMaxYMin: Forces uniform scaling. Align the <min-x>+<width> of the element's viewBox with the maximum X value of the viewport. Align the <min-y> of the element's viewBox with the smallest Y value of the viewport.
xMinYMid: Forces uniform scaling. Align the <min-x> of the element's viewBox with the smallest X value of the viewport. Align the midpoint Y value of the element's viewBox with the midpoint Y value of the viewport.
xMidYMid: Forces uniform scaling. Align the midpoint X value of the element's viewBox with the midpoint X value of the viewport. Align the midpoint Y value of the element's viewBox with the midpoint Y value of the viewport. This is the default value.
xMaxYMid: Forces uniform scaling. Align the <min-x>+<width> of the element's viewBox with the maximum X value of the viewport. Align the midpoint Y value of the element's viewBox with the midpoint Y value of the viewport.
xMinYMax: Forces uniform scaling. Align the <min-x> of the element's viewBox with the smallest X value of the viewport. Align the <min-y>+<height> of the element's viewBox with the maximum Y value of the viewport.
xMidYMax: Forces uniform scaling. Align the midpoint X value of the element's viewBox with the midpoint X value of the viewport. Align the <min-y>+<height> of the element's viewBox with the maximum Y value of the viewport.
xMaxYMax: Forces uniform scaling. Align the <min-x>+<width> of the element's viewBox with the maximum X value of the viewport. Align the <min-y>+<height> of the element's viewBox with the maximum Y value of the viewport.

The following two keywords determine how the SVG should be scaled relative to the container's bounds. Specifying the meet or slice reference is optional and, if provided, it must be one only one of two keywords. meet is the default value.

meet

Scales the graphic such that:

The aspect ratio is preserved.
The entire viewBox is visible within the viewport.
The viewBox is scaled up as much as possible, while still meeting the other criteria.

In this case, if the aspect ratio of the graphic does not match the viewport, some of the viewport will extend beyond the bounds of the viewBox (i.e., the area into which the viewBox will draw will be smaller than the viewport).

slice

Scales the graphic such that:

The aspect ratio is preserved.
The entire viewport is covered by the viewBox.
The viewBox is scaled down as much as possible, while still meeting the other criteria.

In this case, if the aspect ratio of the viewBox does not match the viewport, some of the viewBox will extend beyond the bounds of the viewport (i.e., the area into which the viewBox will draw is larger than the viewport).

Examples

Using `meet` when width > height

This example shows the use of meet when the element's width is greater than its height. It presents three variations, with three different alignment values: xMidYMid, xMinYMid, and xMaxYMid.

html,
body,
svg {
  height: 100%;
}

/* place flex element on each iframe body for responsiveness at different screen sizes */
body {
  display: flex;
}

html

<svg viewBox="-1 -1 202 40" xmlns="http://www.w3.org/2000/svg">
  <defs>
    <path
      id="smiley"
      d="M50,10 A40,40,1,1,1,50,90 A40,40,1,1,1,50,10 M30,40 Q36,35,42,40 M58,40 Q64,35,70,40 M30,60 Q50,75,70,60 Q50,75,30,60" />
  </defs>
</svg>

html

<rect x="0" y="0" width="60" height="30">
  <title>xMidYMid meet</title>
</rect>
<svg
  viewBox="0 0 100 100"
  width="60"
  height="30"
  preserveAspectRatio="xMidYMid meet"
  x="0"
  y="0">
  <use href="#smiley" />
</svg>

html

<rect x="70" y="0" width="60" height="30">
  <title>xMinYMid meet</title>
</rect>
<svg
  viewBox="0 0 100 100"
  width="60"
  height="30"
  preserveAspectRatio="xMinYMid meet"
  x="70"
  y="0">
  <use href="#smiley" />
</svg>

html

  <rect x="140" y="0" width="60" height="30">
    <title>xMaxYMid meet</title>
  </rect>
  <svg
    viewBox="0 0 100 100"
    width="60"
    height="30"
    preserveAspectRatio="xMaxYMid meet"
    x="140"
    y="0">
    <use href="#smiley" />
  </svg>
</svg>

css

path {
  fill: yellow;
  stroke: black;
  stroke-width: 8px;
  stroke-linecap: round;
  stroke-linejoin: round;
  pointer-events: none;
}

rect:hover,
rect:active {
  outline: 1px solid red;
}

Using `slice` when width > height

This example shows the use of slice when the element's width is greater than its height. It presents three variations, with three different alignment values: xMidYMin, xMidYMid, and xMidYMax.

html,
body,
svg {
  height: 100%;
}

/* place flex element on each iframe body for responsiveness at different screen sizes */
body {
  display: flex;
}

html

<svg viewBox="-1 -1 202 57" xmlns="http://www.w3.org/2000/svg">
  <defs>
    <path
      id="smiley"
      d="M50,10 A40,40,1,1,1,50,90 A40,40,1,1,1,50,10 M30,40 Q36,35,42,40 M58,40 Q64,35,70,40 M30,60 Q50,75,70,60 Q50,75,30,60" />
  </defs>
</svg>

html

<rect x="0" y="15" width="60" height="30">
  <title>xMidYMin slice</title>
</rect>
<svg
  viewBox="0 0 100 100"
  width="60"
  height="30"
  preserveAspectRatio="xMidYMin slice"
  x="0"
  y="15">
  <use href="#smiley" />
</svg>

html

<rect x="70" y="15" width="60" height="30">
  <title>xMidYMid slice</title>
</rect>
<svg
  viewBox="0 0 100 100"
  width="60"
  height="30"
  preserveAspectRatio="xMidYMid slice"
  x="70"
  y="15">
  <use href="#smiley" />
</svg>

html

  <rect x="140" y="15" width="60" height="30">
    <title>xMidYMax slice</title>
  </rect>
  <svg
    viewBox="0 0 100 100"
    width="60"
    height="30"
    preserveAspectRatio="xMidYMax slice"
    x="140"
    y="15">
    <use href="#smiley" />
  </svg>
</svg>

css

path {
  fill: yellow;
  stroke: black;
  stroke-width: 8px;
  stroke-linecap: round;
  stroke-linejoin: round;
  pointer-events: none;
}

rect:hover,
rect:active {
  outline: 1px solid red;
}

Using `meet` when height > width

This example shows the use of meet when the element's height is greater than its width. It presents three variations, with three different alignment values: xMidYMin, xMidYMid, and xMidYMax.

html,
body,
svg {
  height: 100%;
}

/* place flex element on each iframe body for responsiveness at different screen sizes */
body {
  display: flex;
}

html

<svg viewBox="-1 -1 202 80" xmlns="http://www.w3.org/2000/svg">
  <defs>
    <path
      id="smiley"
      d="M50,10 A40,40,1,1,1,50,90 A40,40,1,1,1,50,10 M30,40 Q36,35,42,40 M58,40 Q64,35,70,40 M30,60 Q50,75,70,60 Q50,75,30,60" />
  </defs>
</svg>

html

  <rect x=0" y="0" width="30" height="75">
    <title>xMidYMin meet</title>
  </rect>
  <svg
    viewBox="0 0 100 100"
    width="30"
    height="75"
    preserveAspectRatio="xMidYMin meet"
    x="0"
    y="0">
    <use href="#smiley" />
  </svg>

html

<rect x="35" y="0" width="30" height="75">
  <title>xMidYMid meet</title>
</rect>
<svg
  viewBox="0 0 100 100"
  width="30"
  height="75"
  preserveAspectRatio="xMidYMid meet"
  x="35"
  y="0">
  <use href="#smiley" />
</svg>

html

  <rect x="70" y="0" width="30" height="75">
    <title>xMidYMax meet</title>
  </rect>
  <svg
    viewBox="0 0 100 100"
    width="30"
    height="75"
    preserveAspectRatio="xMidYMax meet"
    x="70"
    y="0">
    <use href="#smiley" />
  </svg>
</svg>

css

path {
  fill: yellow;
  stroke: black;
  stroke-width: 8px;
  stroke-linecap: round;
  stroke-linejoin: round;
  pointer-events: none;
}

rect:hover,
rect:active {
  outline: 1px solid red;
}

Using `slice` when height > width

This example shows the use of slice when the element's height is greater than its width. It presents three variations, with three different alignment values: xMinYMid, xMidYMid, and xMaxYMid.

html,
body,
svg {
  height: 100%;
}

/* place flex element on each iframe body for responsiveness at different screen sizes */
body {
  display: flex;
}

html

<svg viewBox="-1 -1 202 80" xmlns="http://www.w3.org/2000/svg">
  <defs>
    <path
      id="smiley"
      d="M50,10 A40,40,1,1,1,50,90 A40,40,1,1,1,50,10 M30,40 Q36,35,42,40 M58,40 Q64,35,70,40 M30,60 Q50,75,70,60 Q50,75,30,60" />
  </defs>
</svg>

html

<rect x="0" y="0" width="30" height="75">
  <title>xMinYMid slice</title>
</rect>
<svg
  viewBox="0 0 100 100"
  width="30"
  height="75"
  preserveAspectRatio="xMinYMid slice"
  x="0"
  y="0">
  <use href="#smiley" />
</svg>

html

<rect x="35" y="0" width="30" height="75">
  <title>xMidYMid slice</title>
</rect>
<svg
  viewBox="0 0 100 100"
  width="30"
  height="75"
  preserveAspectRatio="xMidYMid slice"
  x="35"
  y="0">
  <use href="#smiley" />
</svg>

html

  <rect x="70" y="0" width="30" height="75">
    <title>xMaxYMid slice</title>
  </rect>
  <svg
    viewBox="0 0 100 100"
    width="30"
    height="75"
    preserveAspectRatio="xMaxYMid slice"
    x="70"
    y="0">
    <use href="#smiley" />
  </svg>
</svg>

css

path {
  fill: yellow;
  stroke: black;
  stroke-width: 8px;
  stroke-linecap: round;
  stroke-linejoin: round;
  pointer-events: none;
}

rect:hover,
rect:active {
  outline: 1px solid red;
}

Using the `none` alignment value

This example shows an element with the alignment value set to none.

html,
body,
svg {
  height: 100%;
}

/* place flex element on each iframe body for responsiveness at different screen sizes */
body {
  display: flex;
}

html

<svg viewBox="-1 -1 192 62" xmlns="http://www.w3.org/2000/svg">
  <defs>
    <path
      id="smiley"
      d="M50,10 A40,40,1,1,1,50,90 A40,40,1,1,1,50,10 M30,40 Q36,35,42,40 M58,40 Q64,35,70,40 M30,60 Q50,75,70,60 Q50,75,30,60" />
  </defs>
</svg>

html

  <!-- none -->
  <rect x="0" y="0" width="160" height="60">
    <title>none</title>
  </rect>
  <svg
    viewBox="0 0 100 100"
    width="160"
    height="60"
    preserveAspectRatio="none"
    x="0"
    y="0">
    <use href="#smiley" />
  </svg>
</svg>

css

path {
  fill: yellow;
  stroke: black;
  stroke-width: 8px;
  stroke-linecap: round;
  stroke-linejoin: round;
  pointer-events: none;
}

rect:hover,
rect:active {
  outline: 1px solid red;
}

Elements

You can use this attribute with the following SVG elements:

feImage

For <feImage>, preserveAspectRatio defines how the referenced image should fit in the rectangle define by the <feImage> element.

Value	<align> <meetOrSlice>?
Default value	`xMidYMid` `meet`
Animatable	Yes

image

For <image>, preserveAspectRatio defines how the referenced image should fit in the rectangle define by the <image> element.

Value	<align> <meetOrSlice>?
Default value	`xMidYMid` `meet`
Animatable	Yes

marker

For <marker>, preserveAspectRatio indicates if a uniform scaling must be performed to fit the element viewport.

Value	<align> <meetOrSlice>?
Default value	`xMidYMid` `meet`
Animatable	Yes

pattern

For <pattern>, preserveAspectRatio indicates if a uniform scaling must be performed to fit the element viewport.

Value	<align> <meetOrSlice>?
Default value	`xMidYMid` `meet`
Animatable	Yes

svg

For <svg>, preserveAspectRatio indicates if a uniform scaling must be performed to fit the element viewport.

Value	<align> <meetOrSlice>?
Default value	`xMidYMid` `meet`
Animatable	Yes

symbol

For <symbol>, preserveAspectRatio indicates if a uniform scaling must be performed to fit the element viewport.

Value	<align> <meetOrSlice>?
Default value	`xMidYMid` `meet`
Animatable	Yes

view

For <view>, preserveAspectRatio indicates if a uniform scaling must be performed to fit the element viewport.

Value	<align> <meetOrSlice>?
Default value	`xMidYMid` `meet`
Animatable	Yes

Specifications

Specification
Filter Effects Module Level 1 # element-attrdef-feimage-preserveaspectratio
Scalable Vector Graphics (SVG) 2 # PreserveAspectRatioAttribute