Google Reveals How It Chooses Search & Discover Thumbnails
▼ Summary
– Google updated its documentation to clarify how publishers can specify a preferred image for thumbnails in Search and Discover using metadata.
– Publishers can signal a preferred image through three methods: the schema.org `primaryImageOfPage` property, an `image` property on the page’s main entity, or the `og:image` meta tag.
– Google recommends choosing a relevant, high-resolution image and avoiding generic logos, text-heavy images, or images with extreme aspect ratios.
– For Discover, using this metadata can influence thumbnail selection but does not replace the requirement for `max-image-preview:large` or AMP to enable large image previews.
– This update is a clarification of existing practices, confirming Google uses these metadata signals and providing code examples for implementation.
Understanding how to influence the image Google selects for your search listings and Discover feed is a key part of modern SEO. Google has recently clarified its official guidance, detailing the specific metadata signals publishers can use to suggest a preferred thumbnail. This update provides a clearer roadmap for webmasters aiming to optimize their visual presence in search results.
The company enhanced its Image SEO best practices page with a new segment titled “Specify a preferred image with metadata.” A corresponding update was made to the Discover documentation, linking to the same technical advice. According to Google, these revisions were implemented in response to user feedback to explicitly state that both schema.org structured data and the Open Graph `og:image` meta tag are considered when the system picks an image preview.
The fresh documentation explains that Google’s thumbnail selection is an automated process that evaluates multiple images on a page. To guide this choice, publishers now have three clear methods to specify a favored image. The first approach involves using the `primaryImageOfPage` property within a `WebPage` schema type. The second method attaches an `image` property to the page’s primary entity, using `mainEntity` or `mainEntityOfPage`. The third, and often most familiar, technique is to implement the standard `og:image` meta tag in the HTML head.
Google’s documentation includes practical code examples for each option. For instance, the `primaryImageOfPage` property would be placed inside a JSON-LD structured data block pointing to an image URL. When using the main entity method, the image property is nested within a specific content type schema, such as `BlogPosting`. The guidance also outlines best practices for selecting this preferred image. The image should be highly relevant and truly representative of the page’s content. Publishers are advised to steer clear of generic images like site logos and to avoid images containing extensive text when using these markup methods. Images with extreme aspect ratios, either too narrow or excessively wide, are also discouraged, while high-resolution files are recommended.
The Discover documentation received a parallel update, now recommending the use of either schema.org markup or the `og:image` tag to indicate a large image for Discover thumbnails. It’s important to note that large image previews in Discover require the `max-image-preview:large` setting or an AMP page; the metadata alone does not fulfill this eligibility requirement. The update also reinforced existing advice against using generic or text-heavy images in the specified metadata, directly linking these recommendations to the new technical methods.
This clarification builds upon a broader set of revisions made to the Discover documentation earlier in the year, which focused on content quality, user experience, and imagery. The latest changes specifically expand the image-related section of that guidance.
For website owners and SEO professionals, this update is significant because it explicitly confirms the metadata sources Google utilizes. The documents now provide two concrete technical pathways, schema.org and Open Graph, to signal a preferred thumbnail. Existing recommendations, such as using images at least 1,200 pixels wide with a 16:9 aspect ratio and high resolution, remain crucial. The new section simply explains how to point Google toward an image that already meets these specifications, thereby increasing the likelihood it will be selected.
If you are already implementing `og:image` tags or relevant schema.org properties, this update serves as a confirmation that Google recognizes them. For those not yet using these methods, the provided code examples offer a straightforward starting point. Ultimately, this document change is a clarification of existing processes rather than an announcement of new functionality. Websites seeking greater control over their search result thumbnails should review the new guidance to ensure their current markup aligns with Google’s clarified recommendations.
(Source: Search Engine Journal)
