What thumbnail data does Google require for VideoObject markup?

Definition: VideoObject is structured data that describes a video on a web page. As of 17 October 2026, Google requires its thumbnailUrl property to identify the video's thumbnail image, which must meet Google's image specifications and be accessible to its crawlers.

Key facts

• Google's VideoObject documentation lists thumbnailUrl among the required properties and allows repeated URL values.
• Google's video SEO guide sets a minimum thumbnail size of 60 by 30 pixels and prefers larger images.
• Google's structured data guidelines require image URLs in markup to be crawlable and indexable.
• Google's Video indexing report help identifies thumbnail problems including unsupported formats, invalid sizes and robots.txt blocking.

What goes in thumbnailUrl?

Google's required properties table describes thumbnailUrl as a URL pointing to the video's unique thumbnail image file.

The following JSON fragment reproduces the thumbnail portion of Google's standard video example. It belongs inside a VideoObject and needs the other required properties to form a complete example:

"thumbnailUrl": [
  "https://example.com/photos/1x1/photo.jpg",
  "https://example.com/photos/4x3/photo.jpg",
  "https://example.com/photos/16x9/photo.jpg"
]

These are example image addresses to replace with the video's actual thumbnails. Google's table labels the property as repeatable, so it can contain multiple image URLs.

Which image requirements apply?

Google's thumbnail specifications accept BMP, GIF, JPEG, PNG, WebP, SVG and AVIF. The minimum dimensions are 60 by 30 pixels, with larger images preferred. Google also sets a transparency threshold: at least 80% of the image's pixels must have an alpha value greater than 250, where alpha measures transparency.

The image file must remain available at a stable URL. Google requires access for Googlebot and its image crawler, without robots.txt blocking or a login requirement. Its guidance calls for a unique, stable thumbnail URL for each video and warns that frequently changing thumbnail URLs can prevent successful video indexing.

Google's image rules for structured data also require relevance to the page. Crawlability and indexability apply to every image URL supplied in the markup.

How can thumbnail problems be checked?

Google's VideoObject setup instructions recommend validating the markup with the Rich Results Test and fixing critical errors. For a deployed page, the instructions also recommend URL Inspection to check how Google sees it.

The Video indexing report separates image problems into named reasons. For example, “Thumbnail blocked by robots.txt” identifies a crawling restriction, while “Unsupported thumbnail format” concerns the image format and its file extension. “Invalid thumbnail size” points to dimensions. Selecting a reason opens example pages affected by that issue.

Related terms

• Structured data
• Googlebot-Image
• robots.txt
• How do I add key moments to a video with structured data?

FAQ

Can a thumbnail be hosted on another website?

Google's Video indexing report guidance addresses images hosted on another site. If that host blocks the image, you can ask it to remove the restriction or supply another thumbnail URL that Google can access without logging in.

How can I check a corrected page immediately?

In Google's URL Inspection tool, you can select Test live URL. This fetches and examines the current URL in real time.

Sources

1. Google Search Central, "Video (VideoObject, Clip, BroadcastEvent) structured data", updated 24 September 2026
2. Google Search Central, "Video SEO best practices", updated 18 December 2025
3. Google Search Central, "General structured data guidelines", updated 10 July 2026
4. Google Search Console Help, "Video indexing report", undated
5. Google Search Console Help, "URL Inspection tool", undated

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