Google updates image SEO: How to influence your thumbnails in Search and Discover
Google updates image SEO – and it's more interesting than it sounds
Google has just updated their documentation on image SEO best practices. On the surface, there are no new technical capabilities – but an important clarification has been made.
Google's selection of image previews for both Search and Discover is still fully automated and based on a range of signals. However, in the latest update, Google now describes more directly that you can actually influence which image you prefer to be used as a thumbnail. This is done via metadata.
Two concrete inputs: schema markup and og:image
Google specifically mentions two sources that can serve as inputs to their thumbnail selection:
Schema markup
og:image (Open Graph)
What's interesting is not that these techniques exist – we've known about them for a long time.
What's interesting is that Google now explicitly describes them as signals in the selection of preview images in both Search and Discover. That makes them far more strategic.
What does this mean in practice?
If you work with SEO and content, this means you can now to a greater extent:
Specify a primaryImageOfPage in your schema
Specify image in your structured data
Define a clear and optimised og:image
It is still Google that makes the final decision. But you are giving the algorithm a clearer hint about which image best represents the page.
And in a SERP environment where visual elements are becoming increasingly prominent – especially in Discover – the thumbnail can have a direct impact on CTR.
How significant is the effect in reality?
This is where it gets interesting.
The options are not new. But now that Google highlights them as direct inputs, it opens up an obvious test case:
Does CTR change when primaryImageOfPage is consistently specified?
Is Discover more sensitive to og:image?
Do we see a greater effect on mobile than desktop?
For sites with large amounts of editorial content, e-commerce with product images, or guides where multiple images compete to be selected – it could be the difference between a neutral preview and a converting thumbnail.
Recommendation: Make it systematic
If you are already working with structured data, you should:
Ensure that primaryImageOfPage is correctly implemented
Check that the image field in schema points to the desired image
Validate that og:image matches the visual priority
Test the effect via CTR in GSC and Discover reporting
It does not require significant development resources – but can potentially deliver measurable results.
Conclusion
Google has not changed the algorithm – but they have changed the signal value in their documentation. When they themselves highlight schema markup and og:image as inputs to thumbnail selection, it is a clear indication that these should be taken seriously.
Now it's time to test. Because in an increasingly visual search result, the image may be what determines whether the user clicks – or scrolls on.
