Image Content SEO
When you create image content, give your images descriptive file names so search engines can determine the nature of the image. For example, a file named image0012.png doesn't describe the image, but hockey_helmet.png acts as both the filename and a description. A descriptive file name gives search engines more information about your site.
When you add an image with Site Management Tools (SMT), always include alternate text that describes the image. It's used by screen readers and displayed when the image can't be shown. Enter the alternate text in the Alternate Text field in the Image Settings side panel. These settings display when you add or edit image content.
The default image template file uses the following code to add alternate text and set the image filename on the page. That's how descriptive file names and alternate text give search engines valuable information.
<img src="<%- data.fields.string_src %>"<% if (data.fields.string_alt) { %> alt="<%- data.fields.string_alt %>"<% } %> data-loader="false" />
To view the full default image template, see image_default.txt. If you customize the image template file, make sure you include the alternate text attribute.
Don't use images that are too large, as they can slow down your page. Size your images to fit the areas where you place them. If you want to use an image in both a large area and as a small thumbnail, use two images sized for each area. Don't use a large image in a small area and let it resize automatically.