Web/API/CanvasRenderingContext2D/lineCap

The CanvasRenderingContext2D.lineCap property of the Canvas 2D API determines the shape used to draw the end points of lines.

Note: Lines can be drawn with the stroke(), strokeRect(), and strokeText() methods.

Syntax

ctx.lineCap = "butt" || "round" || "square";

Options

"butt": The ends of lines are squared off at the endpoints. Default value.
"round": The ends of lines are rounded.
"square": The ends of lines are squared off by adding a box with an equal width and half the height of the line's thickness.

Examples

Changing the shape of line caps

This example rounds the end caps of a straight line.

HTML

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

JavaScript

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

ctx.beginPath();
ctx.moveTo(20, 20);
ctx.lineWidth = 15;
ctx.lineCap = 'round';
ctx.lineTo(100, 100);
ctx.stroke();

Result

Comparison of line caps

In this example three lines are drawn, each with a different value for the lineCap property. Two guides to see the exact differences between the three are added. Each of these lines starts and ends exactly on these guides.

The line on the left uses the default "butt" option. It's drawn completely flush with the guides. The second is set to use the "round" option. This adds a semicircle to the end that has a radius half the width of the line. The line on the right uses the "square" option. This adds a box with an equal width and half the height of the line thickness.

<canvas id="canvas" width="150" height="150"></canvas>

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
const lineCap = ['butt', 'round', 'square'];

// Draw guides
ctx.strokeStyle = '#09f';
ctx.beginPath();
ctx.moveTo(10, 10);
ctx.lineTo(140, 10);
ctx.moveTo(10, 140);
ctx.lineTo(140, 140);
ctx.stroke();

// Draw lines
ctx.strokeStyle = 'black';
for (let i = 0; i < lineCap.length; i++) {
  ctx.lineWidth = 15;
  ctx.lineCap = lineCap[i];
  ctx.beginPath();
  ctx.moveTo(25 + i * 50, 10);
  ctx.lineTo(25 + i * 50, 140);
  ctx.stroke();
}

Screenshot	Live sample
[[File:../../../../../../media.prod.mdn.mozit.cloud/attachments/2012/07/09/236/50366ad18b04b40276d6ef95d76281b1/Canvas_linecap.png\|class=internal]]

Specifications

Specification	Status	Comment
HTML Living StandardThe definition of 'CanvasRenderingContext2D.lineCap' in that specification.	Living Standard

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`lineCap`	Chrome Full support Yes	Edge Full support 12	Firefox Full support 1.5	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 4	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes

Legend

Full support: Full support

WebKit/Blink-specific notes

In WebKit- and Blink-based Browsers, a non-standard and deprecated method ctx.setLineCap() is implemented in addition to this property.