Alternative text test
From SiteRay wiki
| SiteRay Test | |
|---|---|
| First appeared: | Sitescore 1.0 |
| Applies to: | All versions |
| Type: | Individual test |
| Scored: | Always |
What does it do?
Checks for use of text equivalents for visual elements (see Alternative text).
Why is it important?
Not including Alternative text means that search engines and users with visual impairments (especially the blind) are unable to identify that content. This is particularly important where an image contains text that is unavailable elsewhere, such as a phone number or company name.
Including Alternative text is one of the most crucial first steps towards making a website accessible, optimised for search engines and compliant. It is also remarkably easy to address. All visual elements of a page should have a text equivalent, for the benefit of those who cannot see the image (e.g. visually impaired or blind), and for search engines, which cannot understand images like people can.
Example results
Note that in this example web addresses have been concealed.
How is it measured?
The use of alternative text is measured for every element of every webpage that could use it (typically images, audio and video). The score is taken from the proportion of alternative text that is specified for each of those elements. A perfect 10 is awarded to sites which specify Alternative text for every appropriate element.
Note that just including anything for Alternative text defies the purpose of this test. Where identified, particularly bad or useless Alternative text is penalised. For example, Alternative text such as "Image01.jpg" does not describe an image to a blind person or search engine.
Technical explanation
Generally, this test is looking for the alt or longdesc attributes on elements such as the <img> tag.
An empty alt attribute is acceptable, but raises a warning (no score penalty is applied). Additional rules test for weak alternative text, such as:
image.jpg (a filename) Click here (assumes use of a mouse, doesn't provide a description) Image or Picture (no actual description)
Some images are automatically excluded, where they are recognised as belonging to an Analytics tool such as WebTrends.
Common problems
Some Analytics tools embed tracking images into your webpages which don’t have alternative text. You can safely amend these to contain an empty alt attribute.
How to improve this score
Wherever possible, specify useful alternative text that describes the visual content. This is a very simple process, and is supported by virtually all Content Management Systems and website editors.
How to use this test effectively
If this score is low, it should be one of the highest priorities for improving search engine placement and accessibility. Adding useful alternative text is not technically difficult or time consuming.
Otherwise, use this test to ensure that alternative text is being applied and to a sufficient standard.
Shortcomings
Because this test is automated, it may not appreciate special context applied to images in a site. For example, it is possible that the most appropriate Alternative text for a given image is "Image", in some rare cases. These instances are generally extremely rare, and great care has been taken to avoid false positives of this nature.
By extension, just because apparently valid Alternative text has been found, does not mean that it is useful for end-users and search engines. You should manually review your Alternative text using SiteRay where possible, in the context of your own site.
