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.

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();
}

ScreenshotLive sample

Specifications

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

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung 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

Legend

Full support  
Full support

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

See also

Document Tags and Contributors

Contributors to this page: mfluehr, fscholz, thatmichael85, nmve, erikadoyle
Last updated by: mfluehr,