@markerHeight : The Marker Viewport Height Attribute

The markerHeight attribute defines the height of the marker viewport - the vertical extent of the coordinate system in which the marker content is rendered. This works in conjunction with markerWidth to establish the complete marker coordinate space.

Usage

The markerHeight attribute is used to:

Define the vertical extent of the marker’s coordinate system
Control the aspect ratio of marker content
Set up proportional marker dimensions
Support responsive marker sizing
Enable data-driven marker height
Coordinate with markerWidth for proper marker proportions

<svg xmlns="http://www.w3.org/2000/svg" width="400" height="200">
    <defs>
        <marker id="arrow" markerWidth="10" markerHeight="10"
                refX="5" refY="5" orient="auto">
            <polygon points="0,0 10,5 0,10" fill="#e74c3c"/>
        </marker>
    </defs>

    <line x1="50" y1="100" x2="350" y2="100"
          stroke="#2c3e50" stroke-width="2"
          marker-end="url(#arrow)"/>
</svg>

Supported Values

Value Type	Description	Example
`<length>`	Positive number (no units)	`markerHeight="10"`
Default	`3` if not specified	(default)

Valid Values

<!-- Common sizes -->
markerHeight="5"    <!-- Short marker -->
markerHeight="10"   <!-- Medium marker -->
markerHeight="20"   <!-- Tall marker -->

<!-- Decimal values -->
markerHeight="12.5"

<!-- Must be positive -->
markerHeight="0"    <!-- Invalid: no viewport -->
markerHeight="-5"   <!-- Invalid: negative not allowed -->

Supported Elements

The markerHeight attribute is supported on:

<marker> - Marker definition element

Data Binding

Dynamic Marker Height

Adjust marker height based on data:

<!-- Model: { markerSize: 14, visualScale: 1.2 } -->
<svg width="400" height="200">
    <defs>
        <marker id="dynamic-marker"
                markerWidth=""
                markerHeight=""
                refX=""
                refY="">
            <circle cx=""
                    cy=""
                    r=""
                    fill="#3498db"/>
        </marker>
    </defs>

    <line x1="50" y1="100" x2="350" y2="100"
          stroke="#2c3e50" stroke-width="2"
          marker-end="url(#dynamic-marker)"/>
</svg>

Proportional Sizing

Scale both dimensions together:

<!-- Model: { scale: 1.5 } -->
<svg width="400" height="200">
    <defs>
        <marker id="scaled-marker"
                markerWidth="10"
                markerHeight="10"
                refX="10"
                refY="5"
                orient="auto">
            <polygon points="0,0 10,5 0,10"
                     fill="#e74c3c"/>
        </marker>
    </defs>

    <line x1="50" y1="100" x2="350" y2="100"
          stroke="#2c3e50" stroke-width="2"
          marker-end="url(#scaled-marker)"/>
</svg>

Variable Aspect Ratios

<!-- Model: {
    markers: [
        { width: 12, height: 8, color: '#e74c3c' },
        { width: 10, height: 10, color: '#3498db' },
        { width: 8, height: 14, color: '#2ecc71' }
    ]
} -->
<svg width="250" height="250">
    <defs>
        <template data-bind="">
            <marker id="marker-"
                    markerWidth=""
                    markerHeight=""
                    refX=""
                    refY="">
                <rect width="" height=""
                      fill="" rx="1"/>
            </marker>
        </template>
    </defs>

    <template data-bind="">
        <line x1="50" y1="50"
              x2="200" y2="50"
              stroke="#2c3e50" stroke-width="2"
              marker-end="url(#marker-)"/>
    </template>
</svg>

Notes

Viewport Coordinate System

The markerHeight defines the vertical coordinate space:

It establishes the vertical range of user units available
Marker content is drawn within this coordinate system (0 to markerHeight)
The actual visual size depends on marker content and markerUnits

<!-- markerHeight=10 means y-coordinates from 0-10 are available -->
<marker id="example" markerWidth="10" markerHeight="10">
    <!-- This circle uses y-coordinates 0-10 -->
    <circle cx="5" cy="5" r="4"/>
</marker>

Aspect Ratio Control

markerWidth and markerHeight together control the aspect ratio:

<!-- Square (1:1) -->
<marker markerWidth="10" markerHeight="10">

<!-- Wide (2:1) -->
<marker markerWidth="20" markerHeight="10">

<!-- Tall (1:2) -->
<marker markerWidth="10" markerHeight="20">

Default Value

If markerHeight is not specified, the default is 3 units:

<!-- These are equivalent -->
<marker id="m1">
<marker id="m2" markerHeight="3">

Reference Point Vertical Positioning

The refY value should coordinate with markerHeight:

<!-- Vertically centered -->
<marker markerWidth="10" markerHeight="10"
        refX="5" refY="5">
    <!-- refY = markerHeight / 2 -->
</marker>

<!-- Top-aligned -->
<marker markerWidth="10" markerHeight="10"
        refX="5" refY="0">
    <!-- refY = 0 for top edge -->
</marker>

<!-- Bottom-aligned -->
<marker markerWidth="10" markerHeight="10"
        refX="5" refY="10">
    <!-- refY = markerHeight for bottom edge -->
</marker>

Scaling Behavior

With markerUnits="strokeWidth", the effective height scales:

<marker markerHeight="3" markerUnits="strokeWidth">
    <!-- stroke-width="2" → effective height = 6 -->
    <!-- stroke-width="4" → effective height = 12 -->
</marker>

Common Patterns

Square marker (arrows, dots):

<marker markerWidth="10" markerHeight="10"
        refX="5" refY="5">
    <circle cx="5" cy="5" r="4"/>
</marker>

Wide marker (horizontal emphasis):

<marker markerWidth="16" markerHeight="8"
        refX="8" refY="4">
    <rect width="16" height="8" rx="2"/>
</marker>

Tall marker (vertical emphasis):

<marker markerWidth="8" markerHeight="16"
        refX="4" refY="8">
    <rect width="8" height="16" rx="2"/>
</marker>

Examples

Square Markers (Equal Width and Height)

<svg width="400" height="200">
    <defs>
        <marker id="square-8" markerWidth="8" markerHeight="8"
                refX="4" refY="4">
            <rect width="8" height="8" fill="#e74c3c"/>
        </marker>
        <marker id="square-12" markerWidth="12" markerHeight="12"
                refX="6" refY="6">
            <rect width="12" height="12" fill="#3498db"/>
        </marker>
        <marker id="square-16" markerWidth="16" markerHeight="16"
                refX="8" refY="8">
            <rect width="16" height="16" fill="#2ecc71"/>
        </marker>
    </defs>

    <line x1="50" y1="50" x2="350" y2="50" stroke="#34495e" stroke-width="2" marker-end="url(#square-8)"/>
    <line x1="50" y1="100" x2="350" y2="100" stroke="#34495e" stroke-width="2" marker-end="url(#square-12)"/>
    <line x1="50" y1="150" x2="350" y2="150" stroke="#34495e" stroke-width="2" marker-end="url(#square-16)"/>
</svg>

Wide Markers (Width > Height)

<svg width="400" height="200">
    <defs>
        <marker id="wide-1" markerWidth="16" markerHeight="8"
                refX="16" refY="4" orient="auto">
            <polygon points="0,0 16,4 0,8" fill="#9b59b6"/>
        </marker>
        <marker id="wide-2" markerWidth="20" markerHeight="10"
                refX="20" refY="5" orient="auto">
            <polygon points="0,0 20,5 0,10" fill="#9b59b6"/>
        </marker>
    </defs>

    <line x1="50" y1="70" x2="350" y2="70" stroke="#34495e" stroke-width="2" marker-end="url(#wide-1)"/>
    <text x="200" y="50" text-anchor="middle" font-size="10">16×8 (2:1 ratio)</text>

    <line x1="50" y1="140" x2="350" y2="140" stroke="#34495e" stroke-width="2" marker-end="url(#wide-2)"/>
    <text x="200" y="120" text-anchor="middle" font-size="10">20×10 (2:1 ratio)</text>
</svg>

Tall Markers (Height > Width)

<svg width="400" height="250">
    <defs>
        <marker id="tall-1" markerWidth="8" markerHeight="16"
                refX="4" refY="8">
            <rect width="8" height="16" fill="#e74c3c" rx="2"/>
        </marker>
        <marker id="tall-2" markerWidth="10" markerHeight="20"
                refX="5" refY="10">
            <rect width="10" height="20" fill="#e74c3c" rx="2"/>
        </marker>
    </defs>

    <line x1="50" y1="80" x2="350" y2="80" stroke="#34495e" stroke-width="2" marker-end="url(#tall-1)"/>
    <text x="200" y="50" text-anchor="middle" font-size="10">8×16 (1:2 ratio)</text>

    <line x1="50" y1="170" x2="350" y2="170" stroke="#34495e" stroke-width="2" marker-end="url(#tall-2)"/>
    <text x="200" y="140" text-anchor="middle" font-size="10">10×20 (1:2 ratio)</text>
</svg>

Circular Markers with Different Heights

<svg width="400" height="250">
    <defs>
        <marker id="circ-6" markerWidth="6" markerHeight="6"
                refX="3" refY="3">
            <circle cx="3" cy="3" r="2.5" fill="#3498db"/>
        </marker>
        <marker id="circ-10" markerWidth="10" markerHeight="10"
                refX="5" refY="5">
            <circle cx="5" cy="5" r="4" fill="#3498db"/>
        </marker>
        <marker id="circ-14" markerWidth="14" markerHeight="14"
                refX="7" refY="7">
            <circle cx="7" cy="7" r="6" fill="#3498db"/>
        </marker>
    </defs>

    <line x1="50" y1="50" x2="350" y2="50" stroke="#34495e" stroke-width="2" marker-end="url(#circ-6)"/>
    <text x="370" y="55" font-size="10">H:6</text>

    <line x1="50" y1="125" x2="350" y2="125" stroke="#34495e" stroke-width="2" marker-end="url(#circ-10)"/>
    <text x="370" y="130" font-size="10">H:10</text>

    <line x1="50" y1="200" x2="350" y2="200" stroke="#34495e" stroke-width="2" marker-end="url(#circ-14)"/>
    <text x="370" y="205" font-size="10">H:14</text>
</svg>

Elliptical Markers (Different Aspect Ratios)

<svg width="400" height="250">
    <defs>
        <marker id="ellipse-1" markerWidth="12" markerHeight="8"
                refX="6" refY="4">
            <ellipse cx="6" cy="4" rx="5" ry="3" fill="#f39c12"/>
        </marker>
        <marker id="ellipse-2" markerWidth="10" markerHeight="10"
                refX="5" refY="5">
            <ellipse cx="5" cy="5" rx="4" ry="4" fill="#f39c12"/>
        </marker>
        <marker id="ellipse-3" markerWidth="8" markerHeight="12"
                refX="4" refY="6">
            <ellipse cx="4" cy="6" rx="3" ry="5" fill="#f39c12"/>
        </marker>
    </defs>

    <line x1="50" y1="50" x2="350" y2="50" stroke="#34495e" stroke-width="2" marker-end="url(#ellipse-1)"/>
    <text x="370" y="55" font-size="9">12×8</text>

    <line x1="50" y1="125" x2="350" y2="125" stroke="#34495e" stroke-width="2" marker-end="url(#ellipse-2)"/>
    <text x="370" y="130" font-size="9">10×10</text>

    <line x1="50" y1="200" x2="350" y2="200" stroke="#34495e" stroke-width="2" marker-end="url(#ellipse-3)"/>
    <text x="370" y="205" font-size="9">8×12</text>
</svg>

Arrow Markers with Varying Heights

<svg width="400" height="300">
    <defs>
        <marker id="arrow-h6" markerWidth="10" markerHeight="6"
                refX="10" refY="3" orient="auto">
            <polygon points="0,0 10,3 0,6" fill="#e74c3c"/>
        </marker>
        <marker id="arrow-h10" markerWidth="10" markerHeight="10"
                refX="10" refY="5" orient="auto">
            <polygon points="0,0 10,5 0,10" fill="#e74c3c"/>
        </marker>
        <marker id="arrow-h14" markerWidth="10" markerHeight="14"
                refX="10" refY="7" orient="auto">
            <polygon points="0,0 10,7 0,14" fill="#e74c3c"/>
        </marker>
    </defs>

    <line x1="50" y1="60" x2="350" y2="60" stroke="#34495e" stroke-width="2" marker-end="url(#arrow-h6)"/>
    <text x="200" y="40" text-anchor="middle" font-size="10">Height: 6 (narrow)</text>

    <line x1="50" y1="150" x2="350" y2="150" stroke="#34495e" stroke-width="2" marker-end="url(#arrow-h10)"/>
    <text x="200" y="130" text-anchor="middle" font-size="10">Height: 10 (balanced)</text>

    <line x1="50" y1="250" x2="350" y2="250" stroke="#34495e" stroke-width="3" marker-end="url(#arrow-h14)"/>
    <text x="200" y="230" text-anchor="middle" font-size="10">Height: 14 (wide)</text>
</svg>

Diamond Markers with Different Heights

<svg width="400" height="250">
    <defs>
        <marker id="diamond-h8" markerWidth="8" markerHeight="8"
                refX="4" refY="4" orient="auto">
            <path d="M 4,0 L 8,4 L 4,8 L 0,4 Z" fill="#2ecc71"/>
        </marker>
        <marker id="diamond-h12" markerWidth="8" markerHeight="12"
                refX="4" refY="6" orient="auto">
            <path d="M 4,0 L 8,6 L 4,12 L 0,6 Z" fill="#2ecc71"/>
        </marker>
        <marker id="diamond-h16" markerWidth="8" markerHeight="16"
                refX="4" refY="8" orient="auto">
            <path d="M 4,0 L 8,8 L 4,16 L 0,8 Z" fill="#2ecc71"/>
        </marker>
    </defs>

    <line x1="50" y1="50" x2="350" y2="50" stroke="#34495e" stroke-width="2" marker-end="url(#diamond-h8)"/>
    <line x1="50" y1="125" x2="350" y2="125" stroke="#34495e" stroke-width="2" marker-end="url(#diamond-h12)"/>
    <line x1="50" y1="205" x2="350" y2="205" stroke="#34495e" stroke-width="2" marker-end="url(#diamond-h16)"/>
</svg>

Star Markers with Proportional Heights

<svg width="400" height="250">
    <defs>
        <marker id="star-h12" markerWidth="12" markerHeight="12"
                refX="6" refY="6">
            <path d="M 6,1 L 7.5,5 L 11,5 L 8.5,7.5 L 9.5,11 L 6,8.5 L 2.5,11 L 3.5,7.5 L 1,5 L 4.5,5 Z"
                  fill="#f1c40f"/>
        </marker>
        <marker id="star-h16" markerWidth="16" markerHeight="16"
                refX="8" refY="8">
            <path d="M 8,1 L 10,6.5 L 15,6.5 L 11,10 L 12.5,15 L 8,11.5 L 3.5,15 L 5,10 L 1,6.5 L 6,6.5 Z"
                  fill="#f1c40f"/>
        </marker>
    </defs>

    <line x1="50" y1="70" x2="350" y2="70" stroke="#34495e" stroke-width="2" marker-end="url(#star-h12)"/>
    <text x="200" y="50" text-anchor="middle" font-size="10">Star: Height 12</text>

    <line x1="50" y1="170" x2="350" y2="170" stroke="#34495e" stroke-width="2" marker-end="url(#star-h16)"/>
    <text x="200" y="150" text-anchor="middle" font-size="10">Star: Height 16</text>
</svg>

Complex Icon with Custom Height

<svg width="400" height="180">
    <defs>
        <marker id="complex" markerWidth="20" markerHeight="24"
                refX="10" refY="12">
            <rect x="2" y="2" width="16" height="20" rx="3" fill="#3498db" stroke="#2980b9" stroke-width="2"/>
            <path d="M 6,12 L 9,15 L 14,10" fill="none" stroke="white" stroke-width="2" stroke-linecap="round"/>
        </marker>
    </defs>

    <line x1="50" y1="90" x2="350" y2="90"
          stroke="#34495e" stroke-width="3"
          marker-end="url(#complex)"/>
    <text x="200" y="50" text-anchor="middle" font-size="12">Complex Icon: 20×24</text>
</svg>

Varying Heights with Same Width

<svg width="400" height="300">
    <defs>
        <marker id="rect-h6" markerWidth="12" markerHeight="6"
                refX="12" refY="3" orient="auto">
            <rect width="12" height="6" fill="#9b59b6" rx="1"/>
        </marker>
        <marker id="rect-h10" markerWidth="12" markerHeight="10"
                refX="12" refY="5" orient="auto">
            <rect width="12" height="10" fill="#9b59b6" rx="1"/>
        </marker>
        <marker id="rect-h16" markerWidth="12" markerHeight="16"
                refX="12" refY="8" orient="auto">
            <rect width="12" height="16" fill="#9b59b6" rx="1"/>
        </marker>
    </defs>

    <line x1="50" y1="50" x2="350" y2="50" stroke="#34495e" stroke-width="2" marker-end="url(#rect-h6)"/>
    <text x="370" y="55" font-size="9">H:6</text>

    <line x1="50" y1="125" x2="350" y2="125" stroke="#34495e" stroke-width="2" marker-end="url(#rect-h10)"/>
    <text x="370" y="130" font-size="9">H:10</text>

    <line x1="50" y1="210" x2="350" y2="210" stroke="#34495e" stroke-width="2" marker-end="url(#rect-h16)"/>
    <text x="370" y="215" font-size="9">H:16</text>
</svg>

Decimal Height Values

<svg width="400" height="150">
    <defs>
        <marker id="decimal-h" markerWidth="12" markerHeight="15.5"
                refX="12" refY="7.75" orient="auto">
            <polygon points="0,0 12,7.75 0,15.5" fill="#e74c3c"/>
        </marker>
    </defs>

    <line x1="50" y1="75" x2="350" y2="75"
          stroke="#34495e" stroke-width="2"
          marker-end="url(#decimal-h)"/>
    <text x="200" y="50" text-anchor="middle" font-size="12">markerHeight="15.5"</text>
</svg>

Gradient Fill with Custom Height

<svg width="400" height="180">
    <defs>
        <linearGradient id="grad-v" x1="0%" y1="0%" x2="0%" y2="100%">
            <stop offset="0%" stop-color="#667eea"/>
            <stop offset="100%" stop-color="#764ba2"/>
        </linearGradient>

        <marker id="gradient-marker" markerWidth="14" markerHeight="18"
                refX="7" refY="9">
            <rect x="1" y="1" width="12" height="16" rx="2"
                  fill="url(#grad-v)" stroke="#5a67d8" stroke-width="1"/>
        </marker>
    </defs>

    <line x1="50" y1="90" x2="350" y2="90"
          stroke="#34495e" stroke-width="3"
          marker-end="url(#gradient-marker)"/>
    <text x="200" y="50" text-anchor="middle" font-size="12">Gradient: 14×18</text>
</svg>

Target with Custom Height Proportions

<svg width="400" height="180">
    <defs>
        <marker id="target-tall" markerWidth="16" markerHeight="20"
                refX="8" refY="10">
            <ellipse cx="8" cy="10" rx="7" ry="9" fill="white" stroke="#e74c3c" stroke-width="2"/>
            <ellipse cx="8" cy="10" rx="4" ry="6" fill="white" stroke="#e74c3c" stroke-width="2"/>
            <ellipse cx="8" cy="10" rx="2" ry="3" fill="#e74c3c"/>
        </marker>
    </defs>

    <line x1="50" y1="90" x2="350" y2="90"
          stroke="#34495e" stroke-width="2"
          marker-end="url(#target-tall)"/>
    <text x="200" y="50" text-anchor="middle" font-size="12">Tall Target: 16×20</text>
</svg>