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The CanvasRenderingContext2D.lineWidth property of the Canvas 2D API sets the thickness of lines in space units. When getting, it returns the current value (1.0 by default). When setting, zero, negative, Infinity and NaN values are ignored; otherwise the current value is set to the new value.

See also the chapter Applying styles and color in the Canvas Tutorial.


ctx.lineWidth = value;


A number specifying the line width in space units. Zero, negative, Infinity and NaN values are ignored.


Using the lineWidth property

This is just a simple code snippet using the lineWidth property to draw lines with a rounded end.


<canvas id="canvas"></canvas>


var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');

ctx.moveTo(0, 0);
ctx.lineWidth = 15;
ctx.lineTo(100, 100);

Edit the code below and see your changes update live in the canvas:


Specification Status Comment
WHATWG HTML Living Standard
The definition of 'CanvasRenderingContext2D.lineWidth' in that specification.
Living Standard  

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)
Feature Android Chrome for Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)
  • In WebKit- and Blink-based Browsers, a non-standard and deprecated method ctx.setLineWidth() is implemented besides this property.

Gecko-specific notes

  • Starting Gecko 2.0 (Firefox 4 / Thunderbird 3.3 / SeaMonkey 2.1), setting lineWidth to a negative value no longer throws an exception; instead, it properly ignores non-positive values.

See also

Document Tags and Contributors

 Contributors to this page: nmve, erikadoyle, fscholz
 Last updated by: nmve,