WebAIM - Web Accessibility In Mind

Quick Reference
Web Accessibility Principles


This resource is designed to be printed as a one page PDF file. An HTML version is also available below.

Principles of Accessibility

  • Perceivable - Available through sight, hearing, or touch.
  • Operable - Compatible with keyboard or mouse.
  • Understandable - User-friendly, easy to comprehend.
  • Robust - Works across browsers, assistive technologies, mobile devices, old devices/browsers, etc. Follows standards.


Provide appropriate alternative text

  • Every non-text element needs a text alternative (alt text) that provides an equivalent to the image content.
  • Alt text should present the content and function, not necessarily a description, of an image.
  • If an image has no relevant content or function, is decorative, or the alternative text is provided in nearby text, then the image should have an empty alternative text value (alt="").
  • If an image is a link (or hotspot), the alt text must describe the link’s function.
  • Avoid words like "picture of," "image of," or "link to."
  • Use the fewest number of words necessary.


Content is well structured and clearly written

  • Use the simplest language appropriate for your content.
  • Organize your content using true headings (e.g., <h1>) and lists.
  • Use empty (white) space to improve readability.
  • Use illustrations, icons, etc. to supplement text.
  • Check spelling, grammar, and readability.

Provide headers for data tables

  • Identify all data table headers using the <th> element.
  • Provide an appropriate scope attribute: <th scope="col"> for column headers or <th scope="row"> for row headers.
  • If appropriate, add a table <caption> for the data table.


Do not rely on color alone to convey meaning

  • The use of color can enhance comprehension, but do not use color alone to convey information. Be especially cautious of red/green color combinations.
  • Make sure that color contrast is strong, especially between text and background.


Ensure users can complete and submit all forms

  • Put form labels adjacent to or near their controls, so the labels are associated visually.
  • Use the <label> element to associate labels and controls.
  • Group similar elements (such as checkboxes or radio buttons) together using <fieldset>.
  • Clearly identify required form elements. Don't make a field required if it is not necessary. Ensure all directions and cues are readily accessible.
  • If there are errors in a form that has been submitted, alert the user in an accessible way (especially to a screen reader user) and make it easy to fix the incorrect information and resubmit the form.


Caption and/or provide transcripts for media

  • Videos and live audio must have captions and a transcript. A transcript is sufficient for archived audio.
  • Captions should be synchronized, equivalent, and accessible.


Ensure accessibility of non-HTML content

  • HTML content will almost always be more accessible than content in any other format.
  • PDF, Microsoft Word and PowerPoint files, OpenOffice.org, and Adobe Flash provide basic accessibility features.
  • Provide accessible alternatives when non-HTML content cannot be made fully accessible.
  • Test the accessibility of non-HTML content in assistive technologies.


  • Ensure that the page is readable and usable when fonts are enlarged 150-200%.
  • Provide a descriptive page <title>.
  • When using scripting, ensure events are available with both mouse and keyboard. Make all scripted content and page updates/changes available to screen readers.
  • Limit pop-up windows and notify users when pop-ups are used.
  • Provide a descriptive title for all frames (e.g., <frame title="navigation">).
  • Follow HTML and CSS coding standards.