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@refY : The Marker Reference Y Position Attribute

The refY attribute defines the vertical reference point of a marker - the Y coordinate within the marker’s coordinate system that aligns with the path vertex. This works with refX to control complete marker positioning relative to the path.

Usage

The refY attribute is used to:

  • Define the vertical anchor point of the marker
  • Control vertical alignment with path vertices
  • Position marker content vertically relative to the path
  • Create properly aligned markers
  • Support data-driven vertical positioning
  • Enable precise marker alignment control
<svg xmlns="http://www.w3.org/2000/svg" width="400" height="200">
    <defs>
        <!-- Arrow with vertical center at path point -->
        <marker id="arrow" 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(#arrow)"/>
</svg>

Supported Values

Value Type Description Example
<length> Number in marker units refY="5"
Default 0 if not specified (default)

Common Values 

<!-- Top edge (0) -->
refY="0"

<!-- Center (markerHeight / 2) -->
refY="5"    <!-- for markerHeight="10" -->

<!-- Bottom edge (markerHeight) -->
refY="10"   <!-- for markerHeight="10" -->

<!-- Decimal values -->
refY="7.5"

<!-- Negative values (outside marker) -->
refY="-2"

Supported Elements

The refY attribute is supported on:

Data Binding

Dynamic Vertical Positioning

Adjust vertical reference based on marker size:

<!-- Model: { markerSize: 14, verticalAlign: 'center' } -->
<svg width="400" height="200">
    <defs>
        <marker id="dynamic-ref"
                markerWidth=""
                markerHeight=""
                refX=""
                refY=""
                orient="auto">
            <polygon points="0,0 , 0,"
                     fill="#3498db"/>
        </marker>
    </defs>

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

Conditional Vertical Alignment 

<!-- Model: { alignToTop: false } -->
<svg width="400" height="200">
    <defs>
        <marker id="aligned-marker"
                markerWidth="10" markerHeight="10"
                refX="5"
                refY=""
                orient="auto">
            <circle cx="5" cy="5" r="4" fill="#e74c3c"/>
        </marker>
    </defs>

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

Data-Driven Vertical Positioning 

<!-- Model: {
    markers: [
        { size: 10, vAlign: 'top', color: '#e74c3c' },
        { size: 12, vAlign: 'center', color: '#3498db' },
        { size: 14, vAlign: 'bottom', color: '#2ecc71' }
    ],
    getRefY: function(m) {
        if (m.vAlign === 'top') return 0;
        if (m.vAlign === 'center') return m.size / 2;
        return m.size;
    }
} -->
<svg width="300" height="250">
    <defs>
        <template data-bind="">
            <marker id="marker-"
                    markerWidth="" markerHeight=""
                    refX=""
                    refY="">
                <circle cx="" cy=""
                        r=""
                        fill=""/>
            </marker>
        </template>
    </defs>

    <template data-bind="">
        <line x1="50" y1="50"
              x2="250" y2="50"
              stroke="#2c3e50" stroke-width="2"
              marker-end="url(#marker-)"/>
    </template>
</svg>

Notes

Reference Point Concept

The refY coordinate within the marker aligns with the path vertex vertically:

<!-- Marker centered vertically -->
<marker markerWidth="10" markerHeight="10" refX="10" refY="5">
    <!-- Point (10, 5) in marker aligns with path vertex -->
    <polygon points="0,0 10,5 0,10"/>
</marker>

Common Vertical Alignment Patterns

Center alignment (most common):

<!-- Marker centered on path -->
<marker markerWidth="10" markerHeight="10"
        refX="5" refY="5">
    <circle cx="5" cy="5" r="4"/>
</marker>

Top alignment:

<!-- Marker's top edge at path -->
<marker markerWidth="10" markerHeight="10"
        refX="5" refY="0">
    <circle cx="5" cy="5" r="4"/>
</marker>

Bottom alignment:

<!-- Marker's bottom edge at path -->
<marker markerWidth="10" markerHeight="10"
        refX="5" refY="10">
    <circle cx="5" cy="5" r="4"/>
</marker>

Relationship with markerHeight

refY should typically be within 0 to markerHeight:

<!-- For markerHeight="10" -->
refY="0"    <!-- Top edge -->
refY="5"    <!-- Center -->
refY="10"   <!-- Bottom edge -->

Default Value

If refY is not specified, the default is 0 (top edge):

<!-- These are equivalent -->
<marker id="m1" markerWidth="10" markerHeight="10">
<marker id="m2" markerWidth="10" markerHeight="10" refY="0">

Coordinate with refX

Both refX and refY work together to define the complete reference point:

<!-- Center-center alignment -->
<marker refX="5" refY="5" markerWidth="10" markerHeight="10">

<!-- Tip-center alignment -->
<marker refX="10" refY="5" markerWidth="10" markerHeight="10">

<!-- Center-bottom alignment -->
<marker refX="5" refY="10" markerWidth="10" markerHeight="10">

Visual Impact

Different refY values change vertical positioning:

<!-- refY="0": marker below path point -->
<marker refY="0">
    <!-- Marker extends downward from point -->
</marker>

<!-- refY="5": marker centered on path point -->
<marker refY="5">
    <!-- Marker straddles the point vertically -->
</marker>

<!-- refY="10": marker above path point -->
<marker refY="10">
    <!-- Marker extends upward to point -->
</marker>

Examples

Vertically Centered Marker (refY = markerHeight / 2) 

<svg width="400" height="150">
    <defs>
        <marker id="centered" markerWidth="10" markerHeight="10"
                refX="10" refY="5" orient="auto">
            <polygon points="0,0 10,5 0,10" fill="#e74c3c"/>
            <circle cx="10" cy="5" r="1" fill="white"/>
        </marker>
    </defs>

    <line x1="50" y1="75" x2="350" y2="75"
          stroke="#34495e" stroke-width="2"
          marker-end="url(#centered)"/>
    <circle cx="350" cy="75" r="3" fill="orange"/>
    <text x="200" y="50" text-anchor="middle" font-size="11">refY="5" (vertically centered)</text>
</svg>

Top-Aligned Marker (refY = 0) 

<svg width="400" height="150">
    <defs>
        <marker id="top-aligned" markerWidth="10" markerHeight="10"
                refX="10" refY="0" orient="auto">
            <polygon points="0,0 10,5 0,10" fill="#3498db"/>
            <circle cx="10" cy="0" r="1" fill="white"/>
        </marker>
    </defs>

    <line x1="50" y1="75" x2="350" y2="75"
          stroke="#34495e" stroke-width="2"
          marker-end="url(#top-aligned)"/>
    <circle cx="350" cy="75" r="3" fill="orange"/>
    <text x="200" y="50" text-anchor="middle" font-size="11">refY="0" (top edge at path)</text>
</svg>

Bottom-Aligned Marker (refY = markerHeight) 

<svg width="400" height="150">
    <defs>
        <marker id="bottom-aligned" markerWidth="10" markerHeight="10"
                refX="10" refY="10" orient="auto">
            <polygon points="0,0 10,5 0,10" fill="#2ecc71"/>
            <circle cx="10" cy="10" r="1" fill="white"/>
        </marker>
    </defs>

    <line x1="50" y1="75" x2="350" y2="75"
          stroke="#34495e" stroke-width="2"
          marker-end="url(#bottom-aligned)"/>
    <circle cx="350" cy="75" r="3" fill="orange"/>
    <text x="200" y="50" text-anchor="middle" font-size="11">refY="10" (bottom edge at path)</text>
</svg>

Comparison of Different refY Values 

<svg width="400" height="300">
    <defs>
        <marker id="ref-y0" markerWidth="10" markerHeight="16"
                refX="10" refY="0" orient="auto">
            <polygon points="0,0 10,8 0,16" fill="#e74c3c"/>
            <circle cx="10" cy="0" r="1.5" fill="white"/>
        </marker>
        <marker id="ref-y8" markerWidth="10" markerHeight="16"
                refX="10" refY="8" orient="auto">
            <polygon points="0,0 10,8 0,16" fill="#3498db"/>
            <circle cx="10" cy="8" r="1.5" fill="white"/>
        </marker>
        <marker id="ref-y16" markerWidth="10" markerHeight="16"
                refX="10" refY="16" orient="auto">
            <polygon points="0,0 10,8 0,16" fill="#2ecc71"/>
            <circle cx="10" cy="16" r="1.5" fill="white"/>
        </marker>
    </defs>

    <line x1="50" y1="60" x2="300" y2="60" stroke="#34495e" stroke-width="2" marker-end="url(#ref-y0)"/>
    <circle cx="300" cy="60" r="3" fill="orange"/>
    <text x="320" y="65" font-size="10">refY="0"</text>

    <line x1="50" y1="150" x2="300" y2="150" stroke="#34495e" stroke-width="2" marker-end="url(#ref-y8)"/>
    <circle cx="300" cy="150" r="3" fill="orange"/>
    <text x="320" y="155" font-size="10">refY="8"</text>

    <line x1="50" y1="240" x2="300" y2="240" stroke="#34495e" stroke-width="2" marker-end="url(#ref-y16)"/>
    <circle cx="300" cy="240" r="3" fill="orange"/>
    <text x="320" y="245" font-size="10">refY="16"</text>
</svg>

Circle with Different Vertical Alignments 

<svg width="400" height="300">
    <defs>
        <marker id="circle-top" markerWidth="12" markerHeight="12"
                refX="6" refY="0">
            <circle cx="6" cy="6" r="5" fill="#9b59b6"/>
            <circle cx="6" cy="0" r="1.5" fill="white" stroke="black" stroke-width="0.5"/>
        </marker>
        <marker id="circle-mid" markerWidth="12" markerHeight="12"
                refX="6" refY="6">
            <circle cx="6" cy="6" r="5" fill="#9b59b6"/>
            <circle cx="6" cy="6" r="1.5" fill="white"/>
        </marker>
        <marker id="circle-bot" markerWidth="12" markerHeight="12"
                refX="6" refY="12">
            <circle cx="6" cy="6" r="5" fill="#9b59b6"/>
            <circle cx="6" cy="12" r="1.5" fill="white" stroke="black" stroke-width="0.5"/>
        </marker>
    </defs>

    <line x1="50" y1="60" x2="300" y2="60" stroke="#34495e" stroke-width="2" marker-end="url(#circle-top)"/>
    <circle cx="300" cy="60" r="3" fill="orange"/>
    <text x="320" y="65" font-size="9">Top</text>

    <line x1="50" y1="150" x2="300" y2="150" stroke="#34495e" stroke-width="2" marker-end="url(#circle-mid)"/>
    <circle cx="300" cy="150" r="3" fill="orange"/>
    <text x="320" y="155" font-size="9">Center</text>

    <line x1="50" y1="240" x2="300" y2="240" stroke="#34495e" stroke-width="2" marker-end="url(#circle-bot)"/>
    <circle cx="300" cy="240" r="3" fill="orange"/>
    <text x="320" y="245" font-size="9">Bottom</text>
</svg>

Diamond with Vertical Alignment Options 

<svg width="400" height="300">
    <defs>
        <marker id="diamond-top" markerWidth="10" markerHeight="12"
                refX="5" refY="0" orient="auto">
            <path d="M 5,0 L 10,6 L 5,12 L 0,6 Z" fill="#f39c12"/>
            <circle cx="5" cy="0" r="1.5" fill="white"/>
        </marker>
        <marker id="diamond-mid" markerWidth="10" markerHeight="12"
                refX="5" refY="6" orient="auto">
            <path d="M 5,0 L 10,6 L 5,12 L 0,6 Z" fill="#f39c12"/>
            <circle cx="5" cy="6" r="1.5" fill="white"/>
        </marker>
        <marker id="diamond-bot" markerWidth="10" markerHeight="12"
                refX="5" refY="12" orient="auto">
            <path d="M 5,0 L 10,6 L 5,12 L 0,6 Z" fill="#f39c12"/>
            <circle cx="5" cy="12" r="1.5" fill="white"/>
        </marker>
    </defs>

    <line x1="50" y1="60" x2="300" y2="60" stroke="#34495e" stroke-width="2" marker-end="url(#diamond-top)"/>
    <circle cx="300" cy="60" r="3" fill="orange"/>

    <line x1="50" y1="150" x2="300" y2="150" stroke="#34495e" stroke-width="2" marker-end="url(#diamond-mid)"/>
    <circle cx="300" cy="150" r="3" fill="orange"/>

    <line x1="50" y1="240" x2="300" y2="240" stroke="#34495e" stroke-width="2" marker-end="url(#diamond-bot)"/>
    <circle cx="300" cy="240" r="3" fill="orange"/>
</svg>

Rectangle with Corner References 

<svg width="400" height="300">
    <defs>
        <marker id="rect-tl" markerWidth="12" markerHeight="10"
                refX="0" refY="0">
            <rect width="12" height="10" fill="#e74c3c"/>
            <circle cx="0" cy="0" r="1.5" fill="white" stroke="black" stroke-width="0.5"/>
        </marker>
        <marker id="rect-mc" markerWidth="12" markerHeight="10"
                refX="6" refY="5">
            <rect width="12" height="10" fill="#3498db"/>
            <circle cx="6" cy="5" r="1.5" fill="white"/>
        </marker>
        <marker id="rect-br" markerWidth="12" markerHeight="10"
                refX="12" refY="10">
            <rect width="12" height="10" fill="#2ecc71"/>
            <circle cx="12" cy="10" r="1.5" fill="white" stroke="black" stroke-width="0.5"/>
        </marker>
    </defs>

    <line x1="50" y1="60" x2="300" y2="60" stroke="#34495e" stroke-width="2" marker-end="url(#rect-tl)"/>
    <circle cx="300" cy="60" r="3" fill="orange"/>
    <text x="320" y="65" font-size="9">TL (0,0)</text>

    <line x1="50" y1="150" x2="300" y2="150" stroke="#34495e" stroke-width="2" marker-end="url(#rect-mc)"/>
    <circle cx="300" cy="150" r="3" fill="orange"/>
    <text x="320" y="155" font-size="9">MC (6,5)</text>

    <line x1="50" y1="240" x2="300" y2="240" stroke="#34495e" stroke-width="2" marker-end="url(#rect-br)"/>
    <circle cx="300" cy="240" r="3" fill="orange"/>
    <text x="320" y="245" font-size="9">BR (12,10)</text>
</svg>

Star with Custom refY 

<svg width="400" height="180">
    <defs>
        <marker id="star-custom" markerWidth="18" markerHeight="18"
                refX="9" refY="12">
            <path d="M 9,1 L 11,7 L 17,7 L 12,11 L 14,17 L 9,13 L 4,17 L 6,11 L 1,7 L 7,7 Z"
                  fill="#f1c40f" stroke="#f39c12" stroke-width="1"/>
            <circle cx="9" cy="12" r="1.5" fill="white"/>
        </marker>
    </defs>

    <line x1="50" y1="90" x2="350" y2="90"
          stroke="#34495e" stroke-width="2"
          marker-end="url(#star-custom)"/>
    <circle cx="350" cy="90" r="3" fill="orange"/>
    <text x="200" y="50" text-anchor="middle" font-size="11">Star with custom refY="12"</text>
</svg>

Ellipse with Vertical Positioning 

<svg width="400" height="300">
    <defs>
        <marker id="ellipse-top" markerWidth="14" markerHeight="20"
                refX="7" refY="0">
            <ellipse cx="7" cy="10" rx="6" ry="9" fill="#3498db"/>
            <circle cx="7" cy="0" r="1.5" fill="white" stroke="black" stroke-width="0.5"/>
        </marker>
        <marker id="ellipse-mid" markerWidth="14" markerHeight="20"
                refX="7" refY="10">
            <ellipse cx="7" cy="10" rx="6" ry="9" fill="#3498db"/>
            <circle cx="7" cy="10" r="1.5" fill="white"/>
        </marker>
        <marker id="ellipse-bot" markerWidth="14" markerHeight="20"
                refX="7" refY="20">
            <ellipse cx="7" cy="10" rx="6" ry="9" fill="#3498db"/>
            <circle cx="7" cy="20" r="1.5" fill="white" stroke="black" stroke-width="0.5"/>
        </marker>
    </defs>

    <line x1="50" y1="60" x2="300" y2="60" stroke="#34495e" stroke-width="2" marker-end="url(#ellipse-top)"/>
    <circle cx="300" cy="60" r="3" fill="orange"/>

    <line x1="50" y1="150" x2="300" y2="150" stroke="#34495e" stroke-width="2" marker-end="url(#ellipse-mid)"/>
    <circle cx="300" cy="150" r="3" fill="orange"/>

    <line x1="50" y1="245" x2="300" y2="245" stroke="#34495e" stroke-width="2" marker-end="url(#ellipse-bot)"/>
    <circle cx="300" cy="245" r="3" fill="orange"/>
</svg>

Decimal refY Value 

<svg width="400" height="150">
    <defs>
        <marker id="decimal-y" markerWidth="10" markerHeight="13"
                refX="10" refY="6.5" orient="auto">
            <polygon points="0,0 10,6.5 0,13" fill="#9b59b6"/>
            <circle cx="10" cy="6.5" r="1.5" fill="white"/>
        </marker>
    </defs>

    <line x1="50" y1="75" x2="350" y2="75"
          stroke="#34495e" stroke-width="2"
          marker-end="url(#decimal-y)"/>
    <circle cx="350" cy="75" r="3" fill="orange"/>
    <text x="200" y="50" text-anchor="middle" font-size="11">Precise: refY="6.5"</text>
</svg>

Negative refY (Outside Marker) 

<svg width="400" height="150">
    <defs>
        <marker id="negative-y" markerWidth="10" markerHeight="10"
                refX="10" refY="-3" orient="auto">
            <polygon points="0,0 10,5 0,10" fill="#e74c3c"/>
            <circle cx="10" cy="-3" r="1.5" fill="white" stroke="black" stroke-width="0.5"/>
        </marker>
    </defs>

    <line x1="50" y1="75" x2="350" y2="75"
          stroke="#34495e" stroke-width="2"
          marker-end="url(#negative-y)"/>
    <circle cx="350" cy="75" r="3" fill="orange"/>
    <text x="200" y="50" text-anchor="middle" font-size="11">Negative refY="-3"</text>
</svg>

Tall Marker with Different refY 

<svg width="400" height="300">
    <defs>
        <marker id="tall-y0" markerWidth="8" markerHeight="20"
                refX="4" refY="0">
            <rect width="8" height="20" rx="2" fill="#2ecc71"/>
            <circle cx="4" cy="0" r="1.5" fill="white" stroke="black" stroke-width="0.5"/>
        </marker>
        <marker id="tall-y10" markerWidth="8" markerHeight="20"
                refX="4" refY="10">
            <rect width="8" height="20" rx="2" fill="#2ecc71"/>
            <circle cx="4" cy="10" r="1.5" fill="white"/>
        </marker>
        <marker id="tall-y20" markerWidth="8" markerHeight="20"
                refX="4" refY="20">
            <rect width="8" height="20" rx="2" fill="#2ecc71"/>
            <circle cx="4" cy="20" r="1.5" fill="white" stroke="black" stroke-width="0.5"/>
        </marker>
    </defs>

    <line x1="50" y1="70" x2="300" y2="70" stroke="#34495e" stroke-width="2" marker-end="url(#tall-y0)"/>
    <circle cx="300" cy="70" r="3" fill="orange"/>

    <line x1="50" y1="150" x2="300" y2="150" stroke="#34495e" stroke-width="2" marker-end="url(#tall-y10)"/>
    <circle cx="300" cy="150" r="3" fill="orange"/>

    <line x1="50" y1="230" x2="300" y2="230" stroke="#34495e" stroke-width="2" marker-end="url(#tall-y20)"/>
    <circle cx="300" cy="230" r="3" fill="orange"/>
</svg>

Complex Icon with Precise Vertical Positioning 

<svg width="400" height="180">
    <defs>
        <marker id="complex-y" 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"/>
            <circle cx="10" cy="12" r="1.5" fill="yellow"/>
        </marker>
    </defs>

    <line x1="50" y1="90" x2="350" y2="90"
          stroke="#34495e" stroke-width="3"
          marker-end="url(#complex-y)"/>
    <circle cx="350" cy="90" r="3" fill="orange"/>
    <text x="200" y="50" text-anchor="middle" font-size="11">Complex icon: refY="12" (vertical center)</text>
</svg>

Gradient Marker with Custom refY 

<svg width="400" height="150">
    <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-y" markerWidth="14" markerHeight="14"
                refX="7" refY="7">
            <circle cx="7" cy="7" r="6" fill="url(#grad-v)" stroke="#5a67d8" stroke-width="1"/>
            <circle cx="7" cy="7" r="1.5" fill="white"/>
        </marker>
    </defs>

    <line x1="50" y1="75" x2="350" y2="75"
          stroke="#34495e" stroke-width="3"
          marker-end="url(#gradient-y)"/>
    <circle cx="350" cy="75" r="3" fill="orange"/>
    <text x="200" y="50" text-anchor="middle" font-size="11">Gradient: refY="7"</text>
</svg>

Offset Vertical Positioning 

<svg width="400" height="300">
    <defs>
        <marker id="offset-top" markerWidth="10" markerHeight="10"
                refX="10" refY="2" orient="auto">
            <polygon points="0,0 10,5 0,10" fill="#e74c3c"/>
            <line x1="0" y1="2" x2="10" y2="2" stroke="white" stroke-width="0.5"/>
        </marker>
        <marker id="offset-mid" markerWidth="10" markerHeight="10"
                refX="10" refY="5" orient="auto">
            <polygon points="0,0 10,5 0,10" fill="#3498db"/>
            <line x1="0" y1="5" x2="10" y2="5" stroke="white" stroke-width="0.5"/>
        </marker>
        <marker id="offset-bot" markerWidth="10" markerHeight="10"
                refX="10" refY="8" orient="auto">
            <polygon points="0,0 10,5 0,10" fill="#2ecc71"/>
            <line x1="0" y1="8" x2="10" y2="8" stroke="white" stroke-width="0.5"/>
        </marker>
    </defs>

    <line x1="50" y1="60" x2="300" y2="60" stroke="#34495e" stroke-width="2" marker-end="url(#offset-top)"/>
    <circle cx="300" cy="60" r="3" fill="orange"/>
    <text x="320" y="65" font-size="9">refY="2"</text>

    <line x1="50" y1="150" x2="300" y2="150" stroke="#34495e" stroke-width="2" marker-end="url(#offset-mid)"/>
    <circle cx="300" cy="150" r="3" fill="orange"/>
    <text x="320" y="155" font-size="9">refY="5"</text>

    <line x1="50" y1="240" x2="300" y2="240" stroke="#34495e" stroke-width="2" marker-end="url(#offset-bot)"/>
    <circle cx="300" cy="240" r="3" fill="orange"/>
    <text x="320" y="245" font-size="9">refY="8"</text>
</svg>

See Also