--- obsoleteMessage: | The `longdesc` attribute is obsolete in the HTML Living Standard, and was never widely supported. Use an `a` element or an image map to link to the description. obsoleteSince: 20 ---

# Using longdesc

ID: H45

Technology: html

Type: Technique

## When to Use

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

## 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.

Authors can provide a description for an image by including text in a separate resource or within the text of the page containing the image. An advantage of using a separate resource for the description is that it is easily reusable for multiple instances of the same image, it does not add on-page visual clutter to the original document, and the description's end-point is apparent to the user. An advantage of providing the description within the same page as the image is that all users can access the description. A limitation of the on-page method, as well as in providing multiple descriptions on a single separate page, is that current implementations supporting longdesc do not identify the long description's end-point. Authors can solve this by providing a well-formed description, which identifies the where the description ends.

## Examples

### Using longdesc to refer to a long description contained on a separate resource.

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

### Using longdesc to refer to a long description within the same page.

    <img longdesc="thispage.html#desc" alt="Line graph of the number of subscribers" src="http://www.company/images/graph.png">
    <div id="desc">
    <h3>Long Description: Line graph of the number of subscribers</h3>
    <!-- Full Description of Graph -->
    <p>Long description ends.</p>
    <div>

## 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

## Related Techniques

- G73
- G74
- G92
- G94

## Resources

- University of Minnesota Duluth listing of longdesc Tools