CanvasRenderingContext2D: shadowBlur property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The CanvasRenderingContext2D.shadowBlur property of the Canvas 2D API specifies the amount of blur applied to shadows. The default is 0 (no blur).

Note: Shadows are only drawn if the shadowColor property is set to a non-transparent value. One of the shadowBlur, shadowOffsetX, or shadowOffsetY properties must be non-zero, as well.

Value

A non-negative float specifying the level of shadow blur, where 0 represents no blur and larger numbers represent increasingly more blur. This value doesn't correspond to a number of pixels, and is not affected by the current transformation matrix. The default value is 0. Negative, Infinity, and NaN values are ignored.

Examples

Adding a shadow to a shape

This example adds a blurred shadow to a rectangle. The shadowColor property sets its color, and shadowBlur sets its level of blurriness.

HTML

html

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

JavaScript

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

// Shadow
ctx.shadowColor = "red";
ctx.shadowBlur = 15;

// Rectangle
ctx.fillStyle = "blue";
ctx.fillRect(20, 20, 150, 100);

Result

Specifications

Specification
HTML Standard # dom-context-2d-shadowblur-dev

Browser compatibility

BCD tables only load in the browser

WebKit/Blink-specific notes

In WebKit- and Blink-based browsers, the non-standard and deprecated method ctx.setShadow() is implemented besides this property.

setShadow(width, height, blur, color, alpha);
setShadow(width, height, blur, graylevel, alpha);
setShadow(width, height, blur, r, g, b, a);
setShadow(width, height, blur, c, m, y, k, a);