Search engines display thumbnail images alongside certain result listings, especially on mobile. A sharp, relevant preview image makes your listing visually dominant and measurably increases the likelihood of a click. This lesson covers how to steer which images get selected and how to maximise their impact.
How Preview Images Are Selected
The thumbnail selection process is automated. The algorithm evaluates every image on your page, weighing factors like dimensions, visual quality, topical relevance to the surrounding text, and prominence in the layout. Testing consistently shows that the largest, highest-quality image positioned near the top of the page is the most likely candidate. You cannot hand-pick the thumbnail directly, but you can stack the deck in your favour through image optimisation and the right meta directives.
Controlling Preview Size with max-image-preview
The max-image-preview robots directive sets an upper limit on how large a thumbnail the search engine is permitted to display for your page. It accepts three values:
- none: Suppresses image previews entirely for the page
- standard: Allows a small, default-sized thumbnail
- large: Permits a full-width preview that spans the result card
For almost every page on your site, "large" is the correct choice. Bigger thumbnails command more visual real estate, particularly on mobile where they significantly boost tap-through rates.
Configuring the Directive on Your Pages
Setting image preview permissions
- 1Open the page in your editor
- 2Access the SEO settings through the page menu
- 3Switch to the Advanced tab
- 4Find the robots meta tag options
- 5Set max-image-preview to "large"
- 6For a site-wide default, apply the same setting through the SEO configuration in your Dashboard for each page type
- 7Publish the changes
Site-Wide Default
Apply max-image-preview:large as the default across all page types through your SEO settings. There is rarely a reason to restrict preview size unless you have specific image licensing concerns.
Making Your Images More Selectable
Give the algorithm strong candidates to choose from by following these practices:
- Place a high-resolution hero image (minimum 1200 pixels wide) at the top of every key page
- Choose images that visually communicate the page topic at a glance, not generic stock patterns
- Write descriptive, keyword-informed alt text for every image on the page
- Set an Open Graph og:image tag to explicitly nominate your preferred visual for sharing and potential thumbnail use
- Compress images for fast loading while preserving visual sharpness, using WebP for the best balance of file size and quality
The Role of Open Graph Images
Although og:image tags are designed for social media link previews, they also serve as a signal to search engines about which image you consider the primary visual identity of the page. Setting a dedicated og:image for each page, sized at a minimum of 1200 by 630 pixels, gives you influence over both social sharing cards and search result thumbnails.
Configuring Open Graph images
- 1Open the page SEO settings in the editor
- 2Navigate to the Social Share tab
- 3Upload or select the image you want as the og:image
- 4Ensure it is at least 1200 by 630 pixels and clearly represents the page content
- 5Preview the social card to confirm the image renders correctly
- 6Save and publish
Ongoing Thumbnail Monitoring
Essential Resources
Google Search Console
Monitor how thumbnails and preview images appear in search results
Facebook Sharing Debugger
Preview and debug Open Graph image tags used for thumbnails
PageSpeed Insights
Optimise image loading performance and Core Web Vitals
Wix SEO Help Centre
Official Wix documentation on social image and preview settings
Search your key pages on a mobile device periodically to see which thumbnails are currently showing. If the algorithm selects a low-quality or irrelevant image, improve your options by adding a stronger hero image, updating the og:image, and confirming the max-image-preview directive is set to large. Changes typically take effect within a few crawl cycles.
Key Takeaways
- Set max-image-preview to "large" across all page types for maximum thumbnail visibility
- Use high-resolution, topically relevant hero images (1200px+ wide) on every important page
- Configure og:image for each page to influence both social previews and search thumbnails
- Check your actual search result thumbnails on mobile devices regularly
- The algorithm selects thumbnails automatically, but your image choices and meta settings heavily influence the outcome
