The stroke-width attribute is a presentation attribute defining the width of the stroke to be applied to the shape.

As a presentation attribute, it can be applied to any element but it only has effect on shapes and text context elements, including: <altGlyph>, <circle>, <ellipse>, <line>, <path>, <polygon>, <polyline>, <rect>, <text>, <textPath>, <tref>, and <tspan>

<svg viewBox="0 0 30 10" xmlns="">
  <!-- Default stroke width: 1 -->
  <circle cx="5" cy="5" r="3" stroke="green" />

  <!-- Stroke width as a number -->
  <circle cx="15" cy="5" r="3" stroke="green"
          stroke-width="3" />

  <!-- Stroke width as a percentage -->
  <circle cx="25" cy="5" r="3" stroke="green"
          stroke-width="2%" />

Usage notes

Value <length> | <percentage>
Default value 1px
Animatable Yes

Note: A percentage value is always computed as a percentage of the normalized viewBox diagonal length.

Browser compatibility

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Specification Status Comment
Scalable Vector Graphics (SVG) 2
The definition of 'stroke-width' in that specification.
Candidate Recommendation Definition for shapes and texts
Scalable Vector Graphics (SVG) 1.1 (Second Edition)
The definition of 'stroke-width' in that specification.
Recommendation Initial definition for shapes and texts