Linked Image Alt Text Acts as Anchor Text
Add alt text to image links as these act as anchor text, including on mobile pages.
Alt Text is Included as Part of the On-page Text
Alt text is shown when images are turned off in a browser and counts as part of the on-page text.
Add Alt Text and Embed Images on Mobile Sites in Preparation for Mobile-First
Google’s Mobile-first team has noticed many sites don’t include alt text for images on mobile sites. John recommends checking that alt text exists for images when checking sites are ready for the switch to Mobile-first indexing as well as making sure images are embedded so they can still appear in Image search.
Add Images to Sitemap to Provide Google With More Information
Images can be added for each page of your site within your sitemap along with captions and alt-tags using special sitemap extensions.
Image Links Pass the Same Weight as Text Links
Provided you have alt text on the image, which is equivalent to the anchor text, image links should be treated the same as text links.
There are no limits to Link Titles, Image Titles and Alt Tags
Title Attribute on Links is Ignored
Google ignores the title attribute in anchor links, but does use alt tags for images inside a link.
Image Alt Text Adds to the Page Content
Adding alt tags adds content to the overall page.