Google updated its image SEO best practices and Google Discover documentation to clarify how Google picks a preferred image thumbnail for Google Search and Google Discover. Google wrote it "uses both schema.org markup and the og:image meta tag as sources when determining image thumbnails in Google Search and Discover."
Google added a whole new section to the image SEO best practices document named Specify a preferred image with metadata. It reads:
Google's selection of an image preview is completely automated and takes into account a number of different sources to select which image on a given page is shown on Google (for example, a text result image or the preview image in Discover).You can influence which image gets selected by providing your preferred image through one of the following metadata sources:
Specify the schema.org primaryImageOfPage property with a URL or ImageObject.
Or specify an image URL or ImageObject property and attach it to the main entity (using the schema.org mainEntity or mainEntityOfPage properties):
Specify the og:image meta tag.
There is also this part for "When choosing your preferred image for use in schema.org markup or the og:image meta tag, follow these best practices:"
- Choose an image that's relevant and representative of the page.
- Avoid using a generic image (for example, your site logo) or an image with text in the schema.org markup or og:image meta tag.
- Avoid using an image with an extreme aspect ratio (such as images that are too narrow or overly wide).
- Use a high resolution, if possible.
Then in the Google Discover documentation, Google expanded on the images section and it reads:
Include compelling, high-quality images in your content that are relevant, especially large images that are more likely to generate visits from Discover. We recommend using images that meet the following specifications: At least 1200 px wide, High resolution (at least 300K), and 16x9 aspect ratio.Google tries to automatically crop the image for use in Discover. If you choose to crop your images yourself, be sure your images are well-cropped and positioned for landscape usage, and avoid automatically applying an aspect ratio. For example, if you crop a vertical image into 16x9 aspect ratio, be sure the important details are included in the cropped version that you specify in the og:image meta tag).
Google also added this section:
Use either schema.org markup or the og:image meta tag to specify a large image that's relevant and representative of the web page, as this can influence which image is chosen as the thumbnail in Discover. Learn more about how to specify your preferred image.
- Avoid using generic images (for example, your site logo) in the schema.org markup or og:image meta tag.
- Avoid using images with text in the schema.org markup or og:image meta tag.
Forum discussion at X.
