Transparent but with no interactive content descendants except for <a> elements, <button> elements, <input> elements whose type attribute is checkbox, radio, or button.
Tag omission
None, both the starting and ending tag are mandatory.
Lets the canvas know whether translucency will be a factor. If the canvas knows there's no translucency, painting performance can be optimized. This is only supported by Mozilla-based browsers; use the standardized canvas.getContext('2d', { alpha: false }) instead.
The width of the coordinate space in CSS pixels. Defaults to 300.
Usage notes
Alternative content
You 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.
Closing </canvas> tag
Unlike the <img> element, the <canvas> element requires the closing tag (</canvas>).
Sizing the canvas using CSS versus HTML
The displayed size of the canvas can be changed using CSS, but if you do this the image is scaled during rendering to fit the styled size, which can make the final graphics rendering end up being distorted.
It is better to specify your canvas dimensions by setting the width and height attributes directly on the <canvas> elements, either directly in the HTML or by using JavaScript.
Maximum canvas size
The maximum size of a <canvas> element is very large, but the exact size depends on the browser. The following is some data we've collected from various tests and other sources (e.g. Stack Overflow):
Browser
Maximum height
Maximum width
Maximum area
Chrome
32,767 pixels
32,767 pixels
268,435,456 pixels (i.e., 16,384 x 16,384)
Firefox
32,767 pixels
32,767 pixels
472,907,776 pixels (i.e., 22,528 x 20,992)
Safari
32,767 pixels
32,767 pixels
268,435,456 pixels (i.e., 16,384 x 16,384)
IE
8,192 pixels
8,192 pixels
?
Note: Exceeding the maximum dimensions or area renders the canvas unusable — drawing commands will not work.
Using an offscreen canvas
A canvas can be rendered using the OffscreenCanvas API where the document and canvas are decoupled. The benefit is that a worker thread can handle canvas rendering and the main thread of your web application is not blocked by canvas operations. By parallelizing work, other UI elements of your web application will remain responsive even if you are running complex graphics on an offscreen canvas. For more information, see the OffscreenCanvas API documentation.
Examples
HTML
This code snippet adds a canvas element to your HTML document. A fallback text is provided if a browser is unable to read or render the canvas.
html
<canvaswidth="120"height="120">
An alternative text describing what your canvas displays.
</canvas>
JavaScript
Then in the JavaScript code, call HTMLCanvasElement.getContext() to get a drawing context and start drawing onto the canvas:
js
const canvas = document.querySelector("canvas");const ctx = canvas.getContext("2d");
ctx.fillStyle ="green";// Add a rectangle at (10, 10) with size 100x100 pixels
ctx.fillRect(10,10,100,100);
Result
Accessibility concerns
Alternative content
The <canvas> element on its own is just a bitmap and does not provide information about any drawn objects. Canvas content is not exposed to accessibility tools as semantic HTML is. In general, you should avoid using canvas in an accessible website or app. The following guides can help to make it more accessible.
1.5["Before Firefox 5, the canvas width and height were signed integers instead of unsigned integers.", "Before Firefox 6, a <canvas> element with a zero width or height would be rendered as if it had default dimensions.", "Before Firefox 12, if JavaScript is disabled, the <canvas> element was being rendered instead of showing the fallback content as per the specification. Since then, the fallback content is rendered instead."]
9
9
2Although 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. Before version 2, Safari will render the content of the fallback in addition to the canvas itself unless you use CSS tricks to mask it.
37
18
4["Before Firefox 5, the canvas width and height were signed integers instead of unsigned integers.", "Before Firefox 6, a <canvas> element with a zero width or height would be rendered as if it had default dimensions.", "Before Firefox 12, if JavaScript is disabled, the <canvas> element was being rendered instead of showing the fallback content as per the specification. Since then, the fallback content is rendered instead."]
10.1
1
1.0
height
1
12
1.5["Before Firefox 5, the canvas width and height were signed integers instead of unsigned integers.", "Before Firefox 6, a <canvas> element with a zero width or height would be rendered as if it had default dimensions.", "Before Firefox 12, if JavaScript is disabled, the <canvas> element was being rendered instead of showing the fallback content as per the specification. Since then, the fallback content is rendered instead."]
9
9
2Although 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. Before version 2, Safari will render the content of the fallback in addition to the canvas itself unless you use CSS tricks to mask it.
37
18
4["Before Firefox 5, the canvas width and height were signed integers instead of unsigned integers.", "Before Firefox 6, a <canvas> element with a zero width or height would be rendered as if it had default dimensions.", "Before Firefox 12, if JavaScript is disabled, the <canvas> element was being rendered instead of showing the fallback content as per the specification. Since then, the fallback content is rendered instead."]
10.1
1
1.0
moz-opaque
No
No
3.5
No
No
No
No
No
4
No
No
No
width
1
12
1.5["Before Firefox 5, the canvas width and height were signed integers instead of unsigned integers.", "Before Firefox 6, a <canvas> element with a zero width or height would be rendered as if it had default dimensions.", "Before Firefox 12, if JavaScript is disabled, the <canvas> element was being rendered instead of showing the fallback content as per the specification. Since then, the fallback content is rendered instead."]
9
9
2Although 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. Before version 2, Safari will render the content of the fallback in addition to the canvas itself unless you use CSS tricks to mask it.
37
18
4["Before Firefox 5, the canvas width and height were signed integers instead of unsigned integers.", "Before Firefox 6, a <canvas> element with a zero width or height would be rendered as if it had default dimensions.", "Before Firefox 12, if JavaScript is disabled, the <canvas> element was being rendered instead of showing the fallback content as per the specification. Since then, the fallback content is rendered instead."]