Alt Tags (alternative tags)_
Alt tags, or ‘alternative tags’, provide a text-based environment so that web crawlers can register the information provided by images on a webpage. It is important to remember that alt tags do not show up on your webpage, which means that your webpage will not become cluttered with excessive text. They can only be seen by customers if they deliberately hover their mouse over the image in question. If for some reason an image will not load, then the alt tag will be presented in the image space and will act as a substitute. Writing effective image alt tags is important for your SEO strategy.
Using alt tags greatly helps those who suffer from sight problems and have their browser read out website content. The browser will be able to read the alt tag as a means of information to identify what your image is. You should remember that alt tags are used for a variety of reasons, such as to provide information for those who surf the web with images turned off, those who have text read aloud to them and for crawling purposes.
What do alt tags look like?
When you hover over an image you may see a line of writing appear, depending on the browser being used and whether a title tag has been used. This will show the alt tag. If you do not see some text appear this could be that the image does not contain an alt tag. An alt tag is a good place to add keywords which are relevant to your webpage. This text should be kept short and to the point rather than a long information box. At the same time, your alt tag should be descriptive of the image.
Using alt tags can slightly benefit your webpage rankings in the SERPs, but also allow your images to be indexed on a broader scale such as in Google image search which can increase traffic.
Applying Alt tags to images
Problems arise when websites use a lot of images and do not include alt tags for them. Subsequently, they will not appear in Google image search and overall rankings could be decreased, though only very slightly. Web crawlers are unable to index images on webpages simply because they do not understand them. So, if your webpage uses a lot of images then you should add alt tags to all of them, in order to help web crawlers rank your website and enable all content to be indexed.
The same principals apply to the use of keywords in alt tags. Keyword stuffing is not encouraged; alt tags should be kept to a few words. If possible, it may be better to include a location or a description instead.