<canvas>

The HTML <canvas> Element can be used to draw graphics via scripting (usually JavaScript). For example, it can be used to draw graphs, make photo compositions or even perform animations. You may (and should) provide alternate content inside the <canvas> block. That content will be rendered both on older browsers that don't support canvas and in browsers with JavaScript disabled.

For more articles on canvas, see the canvas topic page.

Attributes

This element includes the global attributes.

height

The height of the coordinate space in CSS pixels. Defaults to 150.

moz-opaque

Lets the canvas know whether or not translucency will be a factor. If the canvas knows there's no translucency, painting performance can be optimized.

width

The width of the coordinate space in CSS pixels. Defaults to 300.

Description

Required </canvas> tag

Unlike the <img> element, the <canvas> element requires the closing tag (</canvas>).

Sizing the canvas

The displayed size of the canvas can be changed using a stylesheet. The image is scaled during rendering to fit the styled size. If your renderings seem distorted, try specifying your width and height attributes explicitly in the <canvas> attributes, and not using CSS.

Examples

This code snippet adds a canvas element to your HTML document. A fallback text is provided if a browser is unable to render the canvas, or if can't read a canvas. Providing a useful fallback text or sub DOM helps to make the the canvas more accessible.

<canvas id="canvas" width="300" height="300">
  An alternative text describing what your canvas displays. 
</canvas> 

If your canvas does not use transparency set the moz-opaque attribute on the canvas tag. This information can be used internally to optimize rendering. However, this attribute has not been standardized and only works in Mozilla-based rendering engines.

<canvas id="mycanvas" moz-opaque></canvas>

Specifications

Browser compatibility

[1] Before Gecko 5.0 (Firefox 5.0 / Thunderbird 5.0 / SeaMonkey 2.2), the canvas width and height were signed integers instead of unsigned integers.

[2] Prior to Gecko 6.0 (Firefox 6.0 / Thunderbird 6.0 / SeaMonkey 2.3), a <canvas> element with a zero width or height would be rendered as if it had default dimensions.

[3] Before Gecko 12.0 (Firefox 12.0 / Thunderbird 12.0 / SeaMonkey 2.9), if JavaScript is disabled, the <canvas> element was being rendered instead of showing the fallback content as per the specification. Now the fallback content is rendered instead.

[4] See the changelog for Opera 9.0.

[5] Although early versions of Apple's Safari browser don't require the closing tag, the specification indicates that it is required, so you should be sure to include it for broadest compatibility. Those versions of Safari (prior to version 2.0) will render the content of the fallback in addition to the canvas itself unless you use CSS tricks to mask it. Fortunately, users of these versions of Safari are rare nowadays.

See also

• MDN canvas portal
• Canvas tutorial
• Canvas cheat sheet
• Canvas-related demos
• Canvas introduction by Apple