ALT text (alternative text) will display when a web user hovers their cursor over an image that failed to load. The alt text in these cases describes the image in as few words as possible to give the web user an impression of what the picture depicted. This function is also used to help the visually impaired understand what images are shown on a webpage.
Do ALT tags affect SEO?
Alt tags can help improve a webpage’s SEO, if keywords are included in the tag. Keywords associated with certain pages on them rank higher on search engine results pages when those keywords are typed. Keyword stuffing in alt text is considered not to be beneficial to page rank, however.
Alt text also serves another SEO function. As they’re the textual description label for images, they help Google and other search engines present results to image searches. A website’s images can generate clicks from these image searches.