Search engines cannot read text in images, however nice they are, so ‘Alt tags’ are an important way of making your pictures stand out to search engines. The Alt tag should be a brief description of the picture helping the search engine spider to index it and appearing when a user hovers over it with their mouse. It is also useful for the tiny percentage of users that have images disabled or use screen-readers. The table below shows you the pages we have crawled where we have found images with no Alt tags.