In the earlier years of the SEO industry, alt-tags were considered crucial to getting your website on the first page of Google search results. This is no longer the case, since most people have decided that adding keywords to your image’s alt-tags do not impact your rankings. But they’re still important to SEO indirectly.
First of all, what is an alt-tag? An alt-tag is the text that you add to an image that will display when you hover your mouse over the image. Alt-tags are also important for ADA compliance, since it is the alt-tag that is read by screen readers. Screen readers are the way people who are visually impaired or blind browse the internet. When there is an image on the page, the screen reader will convert the alt-tag to speech so that the user can get a sense of what your image is about.
Since an alt-tag is used in this way, leaving it out will impact the user experience on your page for those who are visually impaired. Impacting user experience is a bad thing in SEO, since Google is trying its hardest to predict user behavior.
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