HTML <canvas> Tag
The HTML <canvas>
tag is used for creating graphics on the fly in an HTML document. It can be used for rendering graphs, game graphics, fancy text, or other images.
The tag itself renders a blank canvas. To draw on the canvas, the <canvas>
tag is used in conjunction with JavaScript (using the getContext()
method).
Any content between the <canvas>
</canvas>
tags is "fallback content"- meaning, it will be displayed only if the canvas cannot be displayed.
The <canvas>
tag was introduced in HTML 5.
Syntax
The <canvas>
tag is written as <canvas id="">
</canvas>
with any fallback content inserted between the start and end tag. This fallback content will only be displayed if the browser doesn't support the <canvas>
element.
You can also specify the canvas height and width using the height
and width
attributes respectively. If you don't use these attributes, the canvas will be rendered at the default size, which is a width of 300
and a height of 150
.
To make the <canvas>
actually display something, you will need to add the id
attribute and reference the <canvas>
's id
with some JavaScript.
Like this:
Examples
Shapes
Rectangles
Here's an example of using the <canvas>
element to draw rectangles with various fills and opacity levels.
Bézier Curves
You can also use the <canvas>
element to draw Bézier curves. To do this, use bezierCurveTo
, which works similar to the bezier and path tools in computer drawing packages such as Adobe Illustrator, GIMP, and others.
Text
Here's an example of using the <canvas>
element being used to draw text.
Images
You can even use the <canvas>
element to draw an image. To draw an image, use the drawImage()
method. This requires that you supply the URL of an image.
Attributes
Attributes can be added to an HTML element to provide more information about how the element should appear or behave.
The <canvas>
element accepts the following attributes.
Attribute | Description |
---|---|
width | Specifies the canvas width in pixels. The default value is 300 .
Possible values: [Non-negative integer] (for example, |
height | Specifies the canvas height in pixels. The default value is 150 .
Possible values: [Non-negative integer] (for example, |
Global Attributes
The following attributes are standard across all HTML elements. Therefore, you can use these attributes with the <canvas>
tag , as well as with all other HTML tags.
accesskey
autocapitalize
class
contenteditable
data-*
dir
draggable
hidden
id
inputmode
is
itemid
itemprop
itemref
itemscope
itemtype
lang
part
slot
spellcheck
style
tabindex
title
translate
For a full explanation of these attributes, see HTML 5 global attributes.
Event Handlers
Event handler content attributes enable you to invoke a script from within your HTML. The script is invoked when a certain "event" occurs. Each event handler content attribute deals with a different event.
onabort
onauxclick
onblur
oncancel
oncanplay
oncanplaythrough
onchange
onclick
onclose
oncontextmenu
oncopy
oncuechange
oncut
ondblclick
ondrag
ondragend
ondragenter
ondragexit
ondragleave
ondragover
ondragstart
ondrop
ondurationchange
onemptied
onended
onerror
onfocus
onformdata
oninput
oninvalid
onkeydown
onkeypress
onkeyup
onlanguagechange
onload
onloadeddata
onloadedmetadata
onloadstart
onmousedown
onmouseenter
onmouseleave
onmousemove
onmouseout
onmouseover
onmouseup
onpaste
onpause
onplay
onplaying
onprogress
onratechange
onreset
onresize
onscroll
onsecuritypolicyviolation
onseeked
onseeking
onselect
onslotchange
onstalled
onsubmit
onsuspend
ontimeupdate
ontoggle
onvolumechange
onwaiting
onwheel
Most event handler content attributes can be used on all HTML elements, but some event handlers have specific rules around when they can be used and which elements they are applicable to.
For more detail, see HTML event handler content attributes.