What xAI says about marking
xAI's FAQ says generated images and videos carry a visible Grok watermark, and its usage policy treats removing provenance signals as a violation. Grok Imagine 1.5 went into wide release on 17 June 2026 with image-to-video generation, and the same marking applies.
An undocumented feature is not evidence that it is absent. Check the actual downloaded file for C2PA or other metadata. Platforms can also use watermarks, classifiers and user disclosures, so missing C2PA alone does not tell you whether an image will receive an AI label.
Why check a Grok file anyway
Files pick up metadata as they move: an editing app may add XMP, a phone may add EXIF when you save to the gallery. BlankAI reports exactly what is present, so you know what you are sharing.