The alt tag provides a text based alternative to understanding an image by viewing it. This alt-text is useful to humans when images fail to load and also describe and provide context to search bots trying to interpret the web pages they visit.
Which means that publishing product images on your Magento store without alt tags is a bad idea. Luckily, Magento provides stopgap help for store owners who publish products with blank tags (more about this below). There are however, are many other types of images on an online store that should have well-thought out, descriptive tags.
They are NOT useless pieces of text and besides their SEO functions, they add value for visually impaired users because when available, their screen readers will use them to tell the user what the image is about.
This extends to BUY buttons because a call-to-action button that has a blank alt tag will be skipped by a screen reader instead of telling the user 'Click this button to buy the product'. Which is pretty useful if you are sight impaired!
Although there is speculation that Google can read some images, at this stage it is safest to assume that any images on your site cannot be read or interpreted. Which is why you need to add alt tags to the important images on you store pages.
Consider the image below of interior design website home page.
In the absence of alt text tags, up to 75% of the page contents will be invisible to Google’s search bots. What if the search bots decided that this website was selling holiday accommodation?
The website would then effectively become invisible when prospects searched for ‘interior design’. Not a welcome outcome for the store owner. The solution is to add well thought out alt tag text to all images that are manually placed by the web designer.
Images on a web store can be divided into product images, decorations and call-to-actions. For example, the buy buttons on your product images send signals to search bots about the products you have. Also call-to-action buttons with blank alt tags will be skipped by a screen reader, instead of telling the user 'Click this button to buy the product'. Which is pretty useful if you are sight impaired!
An example of a decorative image is your logo, which appears on all pages. To a search engine, your logo is simply a URL pointing at an image file. Unless you add descriptive alt text to the logo’s properties, the search engine will have no clue to its purpose or value. To update your Magento store logo, go to System – Configuration – Design -Header and add a description for Logo Image alt text.
Not directly. While Google will not penalize a store for missing alt tags, well formed alt-text will improve the Page Quality Score and thus enhance your rankings. There is an article about the value of good alt tags on the Google Webnmasters page that will certainly be worth your while to read. You can find it here: https://support.google.com/webmasters/answer/114016?hl=en
Since it can be a major project to individually script the alt text for each product in an online store, many store owners load their product images without any of this kind of text. This causes Magento to apply a quick fix when displaying these kinds of images. It simply displays the product name as the alt text, which is much better than having empty tags. However, this misses an opportunity to better describe the product to the search bots, which can potentially improve search rankings.
Think about it, if you are selling Duracell triple A batteries then the product name will be ‘Duracell AAA batteries’ as will the alt-text. A quick Google search will bring up around 2 million potential results, which realistically means that your product page has a vanishing low probability of ranking for this product. By adding a unique description to the battery image, you can dramatically increase your changes of being found in a search.
A good option is to make a short list of all your best seller or high return products and then craft alt tags for each one individually. To enter an image alt manually go to Catalog – Products and select a product to edit. On the product details screen, scroll down to Images and Videos and click on an image. The image details screen will pop up with the Alt Text as the first entry point. Add your test here and save the product.
If you want to check your work you must browse to the product page you have just edited, refresh the page and right click on the image. Choose the inspect option and a technical dialog box will open. If you look carefully you should see your newly added alt text appearing in the alt=”” tag.
[Article updated - May 2018 - hjr]