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- WCAG2 SC: 1.1.1. Non-Text -- All non-text content that is presented to the user has a text alternative that serves the equivalent purpose, except for [specific] situations.
- WCAG2 SC: 1.4.5 Images of Text -- If the technologies being used can achieve the visual presentation, text is used to convey information rather than images of text except for [specific situations].
- WCAG2 SC: 4.1.2 Name, Role, Value -- For all user interface components (including but not limited to: form elements, links and components generated by scripts), the name and role can be programmatically determined; states, properties, and values that can be set by the user can be programmatically set; and notification of changes to these items is available to user agents, including assistive technologies.
All meaningful and decorative images must be evaluated. Tests for certain image types are specified.
- Commonly used image formats include .jpg, .png, .svg, .gif, .tiff, .bmp. Other graphic formats are also in use and should be considered for this test.
- Decoration, Formatting, Invisible: If image is pure decoration, is used only for visual formatting, or is not presented to users, then it is implemented in a way that it can be ignored by assistive technology.
- CAPTCHA: If the purpose of the image is to confirm that content is being accessed by a person rather than a computer, then text alternatives that identify and describe the purpose of the image(s) are provided, and alternative forms of CAPTCHA using output modes for different types of sensory perception are provided to accommodate different disabilities.
- Images of text which are essential to the information being conveyed are exempt from SC 1.4.5. Logotypes (text that is part of a logo or brand name) are considered essential.
- The definition of image of text contains the note: "Note: This does not include text that is part of a picture that contains significant other visual content." Examples of such pictures include graphs, screenshots, and diagrams which visually convey important information through more than just text.
- Equivalent descriptions for an image within page text could allow an image to be considered decorative. However, this does not necessitate removal of any accessible text attributes from the image.
- While a longdesc attribute has been used historically to provide extended description for images and is listed as a sufficient technique in WCAG (H45), the technique is not currently well supported for accessibility and is not part of the accessible name or accessible description computation for an image; therefore, this Baseline does not accept the technique.
- The combination of an element's accessible name and accessible description is its text alternative.
Baseline Test ID: 6.1-MeaningfulImage
Identify any image that conveys information (include images of text; functional images used to initiate action, convey meaning, or prompting a response; image maps, etc.).
- Check that the text alternative (combination of the accessible name and accessible description) is not empty. [SC 1.1.1]
- Check that the non-empty text alternative (combination of accessible name and accessible description) provides an equivalent description. Numerous attributes contribute to the computation of the accessible name and accessible description. Refer to HTML Accessibility API Mappings 1.0 for img. [SC 1.1.1]
- Descriptions of the image that are provided by page content must be programmatically associated.
- When an image is updated to convey a new meaning, check that its text alternative is updated at the same time. [SCs 1.1.1 and 4.1.2]
- Check that the ARIA role is NOT "presentation".
- Check that the ARIA role is NOT "none".
- Check that aria-hidden is NOT set to "true".
If any of the above checks fail, then Baseline Test 6.1-MeaningfulImage fails.
Baseline Test ID: 6.2-DecorativeImage
Identify any decorative image that is pure decoration, is used only for visual formatting, or is not presented to users.
Check that at least one of the following is true [SC 1.1.1]:
- The ARIA role is "presentation".
- The ARIA role is "none".
- The aria-hidden is set to "true".
- The text alternative (combination of accessible name and accessible description) is empty (e.g. ""). Numerous attributes contribute to the computation of the accessible name and accessible description. Refer to HTML Accessibility API Mappings 1.0 for img.
- The image is inserted via CSS (e.g., using a background image).
If all of the above checks fail, then Baseline Test 6.2-DecorativeImage fails.
Baseline Test ID: 6.3-Captcha
Identify any CAPTCHA designed to determine if content is being accessed by a person rather than a computer.
- Check that the text alternative (combination of the accessible name and accessible description) is not empty. [SC 1.1.1]
- Check that the non-empty text alternative (combination of accessible name and accessible description) identify and describe the purpose of the CAPTCHA. [SC 1.1.1]
- Check that alternative forms of CAPTCHA are provided, at a minimum, for users without vision and users without hearing. [SC 1.1.1]
If any of the above checks fail, then Baseline Test 6.3-Captcha fails.
Baseline Test ID: 6.4-ImageText
Identify any images of text, except where a particular presentation of text is essential to the information being conveyed (e.g., logotypes or text that is part of a logo or brand name).
- Check that using text cannot achieve the same visual presentation and effect as images of text. [SC 1.4.5]
- Check that the image of text can be visually customized to a user's requirements. [SC 1.4.5].
For example, web content allows users to specify font, size, color, and background settings, and all images of text are then provided based on those settings.
If any of the above checks fail, then Baseline Test 6.4-ImageText fail.
- The following sufficient techniques and/or common failures were considered when developing this test procedure for this baseline requirement:
- ARIA6: Using aria-label to provide labels for objects
- ARIA15: Using aria-describedby to provide descriptions of images
- H36: Using alt attributes on images used as submit buttons
- H37: Using alt attributes on img elements
- H67: Using null alt text and no title attribute on img elements for images that AT should ignore
- G143: Providing a text alternative that describes the purpose of the CAPTCHA
- G144: Ensuring that the Web Page contains another CAPTCHA serving the same purpose using a different modality
- H86: Providing text alternatives for ASCII art, emoticons, and leetspeak
- F30: Failure of Success Criterion 1.1.1 due to using text alternatives that are not alternatives (e.g., filenames or placeholder text)
- F38: Failure of Success Criterion 1.1.1 due to not marking up decorative images in HTML in a way that allows assistive technology to ignore them
- F39: Failure of Success Criterion 1.1.1 due to providing a text alternative that is not null (e.g., alt="spacer" or alt="image") for images that should be ignored by assistive technology
- F65: Failure of Success Criterion 1.1.1 due to omitting the alt attribute or text alternative on img elements, area elements, and input elements of type = "image"
- F20: Failure of Success Criterion 1.1.1 and 4.1.2 due to not updating text alternatives when changes to non-text content occur
- C9: Using CSS to include decorative images