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
HTML Living Standard
The definition of 'CanvasRenderingContext2D.lineWidth' in that specification.
Living Standard  

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic supportChrome Full support YesEdge Full support 12Firefox Full support YesIE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes


Full support  
Full support

  • 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: fscholz, nmve, erikadoyle
Last updated by: fscholz,