Use Alt Tags as Anchor Text when Linking with Images
When using links within images, make sure the alt attribute is being used in order to provide the anchor text that you want associated with the link.
Embedding Images From Other Sources Can Impact Image Search Traffic
Embedding images from other sources via iframes makes it more difficult to index an image alongside a particular page as opposed to an image embedded normally in the HTML. On top of that, sources like Instagram add noimageindex within the embed code which will prevent images from being indexed.
Use the Mobile Friendly Test to Check the Implementation of Lazy Loading
If you are using JSON or JQuery to retrieve images for lazy loading, using the mobile friendly test will allow you to see if these are able to be successfully loaded or not.
When Optimising For Image Search Focus on The User Journey
Rather than just optimising images technically, John recommends focusing more on how a user will search for the visual content on your site.
Google Uses Alt Attribute as Part of Anchor For Linked Images
For linked images, Google sees the alt attribute as a descriptive part of the page it is on, but it is also used as part of the anchor for the page the image is linking to.
For Image Optimization Check Indexing, Deferred Loading Method & Discoverable Links in DOM
For images John recommends looking out for which ones are being indexed, double checking the method for deferred loading and checking links can be discovered by Googlebot in the DOM.
Google Has No Preference Between Text Links & Image Links
Google has adapted to handle all sorts of different organic links, and doesn’t see text links as better than image links.
Decorative Images Don’t Need to be Indexed
Decorative images like stock photos don’t need to be indexed because they won’t provide a useful path for users coming to your site from image search. Instead, focus on images that have value for your business such as product images.
Using Stock Photos Will Not Impact Web Search Rankings
The images used on a page don’t have an impact on normal web search rankings. However, within image search Google typically recognise stock photos which are being used on several different sites and will pick just one to be indexed.