Alt text Access Keys Criterion
The spider will check for alt text on all images (alt="", alt="description"). The manual check will determine whether each alt text correctly represents the image.
- Every image should have alt text properly describing the nature of the image. At the spiderable level we can only check whether or not alt text is present.
- At the manual level we must check the descriptions are appropriate. In the case of list markup - or graphics used as place holders, borders or images not vital to understanding content - the alt text can read <alt="">. In any other case the alt text should, in no more than 1,024 characters, describe the image. For example, alt="company logo", or alt="Samsung D500 mobile phone".
- Ideally, images should have a title="title description" element.
- You can also use the longdesc element if you need more space. For example, use on a site using photographs when you need to describe the pictures in greater detail in order to represent the purpose of the site. One instance might involve photographs of the facilities of a particular resort or a hotel on the website of a travel agency .
- Using alt text properly makes a page accessible to anyone using a text-only browser, browsing with images turned off for speed of loading or using a screen reader.
- Points - At spider level points will be calculated based on the formula t=3p where t=total points scored and p=percentage of images with alt tags.
- At manual level this will be replaced with a new score calculated on the formula t=3c where c=percentage of correct alt tags.
- This criterion has a weighting of three.
- We also take into account the number of images on the site in relation to the number of incorrect or missing alts plus number of images in relation to amount of text. For example, on a site with 500 words of text, two images and one missing or incorrect alt, then an alt is going to be far less problematic than a page with 200 words of text and 100 images with 50 missing or incorrect alts.