Baseline Widely available
Use the HTML <canvas>
element with either the canvas scripting API or the WebGL API to draw graphics and animations.
This element's attributes include the global attributes.
height
The height of the coordinate space in CSS pixels. Defaults to 150.
moz-opaque
Non-standard Deprecated
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.
width
The width of the coordinate space in CSS pixels. Defaults to 300.
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.
</canvas>
tag
Unlike the <img>
element, the <canvas>
element requires the closing tag (</canvas>
).
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.
The exact maximum size of a <canvas>
element depends on the browser and environment. While in most cases the maximum dimensions exceed 10,000 x 10,000 pixels, notably iOS devices limit the canvas size to only 4,096 x 4,096 pixels. See canvas size limits in different browsers and devices.
Note: Exceeding the maximum dimensions or area renders the canvas unusable â drawing commands will not work.
Using an offscreen canvasA 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.
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.
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.
<canvas width="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:
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 Technical summary Specifications Browser compatibility See also
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HTML:
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