Source: Schema.org v30.1 vocabulary. Official thumbnail property definition.
What does thumbnail mean?
Thumbnail image for an image or video.
Used on types (domainIncludes)
Expected value types (rangeIncludes)
Schema.org domainIncludes and rangeIncludes are descriptive guidance, not strict validation prohibitions. Check the official reference for updates.
Related reference
Browse all Schema.org types and properties · Google feature support status