The Graphics Canvas Element - HTML: HyperText Markup Language

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  1. References
  2. HTML
  3. Elements
  4. <canvas>
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    • 中文 (简体)
    • 正體中文 (繁體)
  • Attributes
  • Usage notes
  • Accessibility
  • Examples
  • Technical summary
  • Specifications
  • Browser compatibility
  • See also
  1. HTML
  2. Tutorials
  3. HTML basics
  4. Introduction to HTML
    1. Introduction to HTML overview
    2. Getting started with HTML
    3. What's in the head? Metadata in HTML
    4. HTML text fundamentals
    5. Creating hyperlinks
    6. Advanced text formatting
    7. Document and website structure
    8. Debugging HTML
    9. Assessment: Marking up a letter
    10. Assessment: Structuring a page of content
  5. Multimedia and embedding
    1. Multimedia and embedding overview
    2. Images in HTML
    3. Video and audio content
    4. From object to iframe — other embedding technologies
    5. Adding vector graphics to the web
    6. Responsive images
    7. Assessment: Mozilla splash page
  6. HTML tables
    1. HTML tables overview
    2. HTML table basics
    3. HTML table advanced features and accessibility
    4. Assessment: Structuring planet data
  7. References
  8. HTML elements
    1. <a>
    2. <abbr>
    3. <acronym> Deprecated
    4. <address>
    5. <area>
    6. <article>
    7. <aside>
    8. <audio>
    9. <b>
    10. <base>
    11. <bdi>
    12. <bdo>
    13. <big> Deprecated
    14. <blockquote>
    15. <body>
    16. <br>
    17. <button>
    18. <canvas>
    19. <caption>
    20. <center> Deprecated
    21. <cite>
    22. <code>
    23. <col>
    24. <colgroup>
    25. <data>
    26. <datalist>
    27. <dd>
    28. <del>
    29. <details>
    30. <dfn>
    31. <dialog>
    32. <dir> Deprecated
    33. <div>
    34. <dl>
    35. <dt>
    36. <em>
    37. <embed>
    38. <fencedframe> Experimental
    39. <fieldset>
    40. <figcaption>
    41. <figure>
    42. <font> Deprecated
    43. <footer>
    44. <form>
    45. <frame> Deprecated
    46. <frameset> Deprecated
    47. <h1>
    48. <head>
    49. <header>
    50. <hgroup>
    51. <hr>
    52. <html>
    53. <i>
    54. <iframe>
    55. <img>
    56. <input>
    57. <ins>
    58. <kbd>
    59. <label>
    60. <legend>
    61. <li>
    62. <link>
    63. <main>
    64. <map>
    65. <mark>
    66. <marquee> Deprecated
    67. <menu>
    68. <meta>
    69. <meter>
    70. <nav>
    71. <nobr> Deprecated
    72. <noembed> Deprecated
    73. <noframes> Deprecated
    74. <noscript>
    75. <object>
    76. <ol>
    77. <optgroup>
    78. <option>
    79. <output>
    80. <p>
    81. <param> Deprecated
    82. <picture>
    83. <plaintext> Deprecated
    84. <portal> Experimental
    85. <pre>
    86. <progress>
    87. <q>
    88. <rb> Deprecated
    89. <rp>
    90. <rt>
    91. <rtc> Deprecated
    92. <ruby>
    93. <s>
    94. <samp>
    95. <script>
    96. <search>
    97. <section>
    98. <select>
    99. <slot>
    100. <small>
    101. <source>
    102. <span>
    103. <strike> Deprecated
    104. <strong>
    105. <style>
    106. <sub>
    107. <summary>
    108. <sup>
    109. <table>
    110. <tbody>
    111. <td>
    112. <template>
    113. <textarea>
    114. <tfoot>
    115. <th>
    116. <thead>
    117. <time>
    118. <title>
    119. <tr>
    120. <track>
    121. <tt> Deprecated
    122. <u>
    123. <ul>
    124. <var>
    125. <video>
    126. <wbr>
    127. <xmp> Deprecated
  9. Global attributes
    1. accesskey
    2. anchor Experimental Non-standard
    3. autocapitalize
    4. autocorrect Experimental
    5. autofocus
    6. class
    7. contenteditable
    8. data-*
    9. dir
    10. draggable
    11. enterkeyhint
    12. exportparts
    13. hidden
    14. id
    15. inert
    16. inputmode
    17. is
    18. itemid
    19. itemprop
    20. itemref
    21. itemscope
    22. itemtype
    23. lang
    24. nonce
    25. part
    26. popover
    27. slot
    28. spellcheck
    29. style
    30. tabindex
    31. title
    32. translate
    33. virtualkeyboardpolicy Experimental
    34. writingsuggestions
  10. Attributes
    1. accept
    2. autocomplete
    3. capture
    4. crossorigin
    5. dirname
    6. disabled
    7. elementtiming
    8. for
    9. max
    10. maxlength
    11. min
    12. minlength
    13. multiple
    14. pattern
    15. placeholder
    16. readonly
    17. rel
    18. required
    19. size
    20. step
  11. <input> types
    1. <input type="button">
    2. <input type="checkbox">
    3. <input type="color">
    4. <input type="date">
    5. <input type="datetime-local">
    6. <input type="email">
    7. <input type="file">
    8. <input type="hidden">
    9. <input type="image">
    10. <input type="month">
    11. <input type="number">
    12. <input type="password">
    13. <input type="radio">
    14. <input type="range">
    15. <input type="reset">
    16. <input type="search">
    17. <input type="submit">
    18. <input type="tel">
    19. <input type="text">
    20. <input type="time">
    21. <input type="url">
    22. <input type="week">
  12. Guides
    1. Content categories
    2. Block-level elements
    3. Inline elements
    4. Quirks Mode and Standards Mode
    5. Date and time formats used in HTML
    6. Constraint validation
    7. Microdata
    8. Microformats
    9. Viewport meta tag
    10. Allowing cross-origin use of images and canvas
  • Attributes
  • Usage notes
  • Accessibility
  • Examples
  • Technical summary
  • Specifications
  • Browser compatibility
  • See also

Use the HTML <canvas> element with either the canvas scripting API or the WebGL API to draw graphics and animations.

Attributes

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.

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 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 — 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.

Accessibility

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.

  • Canvas accessibility use cases
  • Canvas element accessibility issues
  • HTML Canvas Accessibility in Firefox 13 – by Steve Faulkner
  • Best practices for interactive canvas elements

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<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:

jsconst 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

Content categories Flow content, phrasing content, embedded content, palpable content.
Permitted content 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.
Permitted parents Any element that accepts phrasing content.
Implicit ARIA role No corresponding role
Permitted ARIA roles Any
DOM interface HTMLCanvasElement

Specifications

Specification
HTML Standard # the-canvas-element

Browser compatibility

BCD tables only load in the browser

See also

  • Canvas API
  • Canvas tutorial
  • OffscreenCanvas
  • Canvas cheat sheet (2009)
  • Canvas cheat sheet (pdf) (2015)
  • Safari HTML canvas guide via Apple (2013)
  • CanvasRenderingContext2D 2D drawing context for a canvas element via Apple.com
  • WebGL API
  • <img>
  • SVG
  • Using HTML audio and video

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