The alt tag, also known as the alt attribute or alt text, is a small piece of HTML code that describes the appearance and function of an image on a webpage. It’s effectively a brief description that you attach to an image in your website’s HTML.
The reason why the alt tag is important for Search Engine Optimization (SEO) is multifaceted. First, it is essential for web accessibility. The World Wide Web Consortium (W3C) in its Web Content Accessibility Guidelines (WCAG) has made it clear that all non-text content should have a text alternative, including images. So, for visually impaired users who use screen readers, or in cases where an image can’t be loaded, this alt text is essential to provide context regarding the image.
Secondly, search engines like Google, Bing, etc., use automated crawlers, also known as spiders or bots, to index the information on the web. However, these crawlers cannot ‘see’ images like humans can. Therefore, the alt tag provides a text description of the image, which can be analyzed by the bots for indexing. Thus, the appropriate use of alt tags can contribute positively to the visibility of your website in search engine rankings.
For instance, if an e-commerce website sells bags and each product image has a relevant alt tag, such as “leather tote bag in black,” it increases the likelihood of the website appearing in image search results for those keywords. Google’s Image Publishing Guidelines even suggest that good URL structure, anchor text, and descriptive tags can make your images and site more discoverable.
Not using alt tags potentially excludes a portion of your website’s audience and can lead to a decrease in site traffic. Moreover, it can hamper the site’s visibility on search engine results, leading to lower SEO ranking.
Ensure your alt tag is brief yet descriptive and try to include relevant keywords. However, avoid keyword stuffing as it can lead to penalties by search engines. An example of a good alt tag is 
.
The sources used for this answer include the W3C’s Web Content Accessibility Guidelines (WCAG), Google’s Image Publishing Guidelines, and SEO best practices from reputable digital marketing websites like Moz, Yoast, and Search Engine Journal.
In conclusion, alt tags play a vital role in SEO by improving web accessibility, enhancing user experience, and increasing your content’s visibility to search engine bots. It’s a small detail that can make a significant difference to your website’s performance on search engine result pages.
