Techniques for WCAG 2.0

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# H45: Using longdesc

## Applicability

HTML and XHTML documents that include images that cannot be described in a short text alternative.

This technique relates to:

- Success Criterion 1.1.1 (Non-text Content)
  - How to Meet 1.1.1 (Non-text Content)
  - Understanding Success Criterion 1.1.1 (Non-text Content)

## User Agent and Assistive Technology Support Notes

Some older assistive technologies do not support the `longdesc` attribute.

## Description

The objective of this technique is to provide information in a file designated by the `longdesc` attribute when a short text alternative does not adequately convey the function or information provided in the image. The `longdesc` attribute is a URI, the target of which contains a long description of the non-text content.

## Examples

### Example 1

Example Code:

    <p><img src="chart.gif" alt="a complex chart" longdesc="chartdesc.html"/></p>

## Resources

Resources are for information purposes only, no endorsement implied.

- Too much accessibility - the rise and fall of the LONGDESC

## Related Techniques

- G73: Providing a long description in another location with a link to it that is immediately adjacent to the non-text content
- G74: Providing a long description in text near the non-text content, with a reference to the location of the long description in the short description
- G92: Providing long description for non-text content that serves the same purpose and presents the same information
- G94: Providing short text alternative for non-text content that serves the same purpose and presents the same information as the non-text content

## Tests

### Procedure

1. Check that the `img` element has a longdesc attribute.

2. Check that the value of the `longdesc` attribute is a valid URI of an existing resource.

3. Check that the content at the target of that URI contains a long description describing the original non-text content associated with it.

### Expected Results

- #1 through #3 are all true

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