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.
Syntax
ctx.lineWidth = value;
Options
value
- A number specifying the line width in space units. Zero, negative,
Infinity
andNaN
values are ignored.
Examples
Using the lineWidth
property
This is just a simple code snippet using the lineWidth
property to draw lines with a rounded end.
HTML
<canvas id="canvas"></canvas>
JavaScript
var canvas = document.getElementById("canvas"); var ctx = canvas.getContext("2d"); ctx.beginPath(); ctx.moveTo(0,0); ctx.lineWidth = 15; ctx.lineTo(100, 100); ctx.stroke();
Edit the code below and see your changes update live in the canvas:
Playable code
<canvas id="canvas" width="400" height="200" class="playable-canvas"></canvas> <div class="playable-buttons"> <input id="edit" type="button" value="Edit" /> <input id="reset" type="button" value="Reset" /> </div> <textarea id="code" class="playable-code"> ctx.beginPath(); ctx.moveTo(0,0); ctx.lineWidth = 15; ctx.lineTo(100, 100); ctx.stroke();</textarea>
var canvas = document.getElementById("canvas"); var ctx = canvas.getContext("2d"); var textarea = document.getElementById("code"); var reset = document.getElementById("reset"); var edit = document.getElementById("edit"); var code = textarea.value; function drawCanvas() { ctx.clearRect(0, 0, canvas.width, canvas.height); eval(textarea.value); } reset.addEventListener("click", function() { textarea.value = code; drawCanvas(); }); edit.addEventListener("click", function() { textarea.focus(); }) textarea.addEventListener("input", drawCanvas); window.addEventListener("load", drawCanvas);
Specifications
Specification | Status | Comment |
---|---|---|
WHATWG HTML Living Standard The definition of 'CanvasRenderingContext2D.lineWidth' in that specification. |
Living Standard |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
WebKit/Blink-specific notes
- 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
- The interface defining it,
CanvasRenderingContext2D
CanvasRenderingContext2D.lineCap
CanvasRenderingContext2D.lineJoin