The max-image-preview robots directive controls the maximum size of image previews that Google may display in search results for a given page. It accepts three values: none, which prevents image previews entirely; standard, which limits previews to small thumbnail sizes; and large, which allows Google to show larger image previews including in mobile search features such as image carousels and Discover. The directive is set via a meta robots tag or X-Robots-Tag header (for example, content=“max-image-preview:large”). Google introduced it in September 2019 alongside max-snippet and max-video-preview to give publishers granular control over how their content is previewed. Setting max-image-preview:large is recommended for sites that want their images considered for Google Discover, as large preview images are a requirement for Discover eligibility according to Google’s documentation. The default behaviour, when no directive is present, is equivalent to standard.