Can competition organizers tell if a photo was edited from metadata or the JPEG file?

Sometimes, but not perfectly. For JPEGs, organizers can often spot signs that a file was edited after capture by checking EXIF/metadata and the JPEG’s internal signature. Editing software may leave telltale clues such as changed timestamps, added software fields, or a JPEG encoding pattern associated with Photoshop or other editors.

However, the rule itself is a bit fuzzy: a straight-out-of-camera JPEG is already processed. The camera applies its own choices for white balance, brightness, saturation, contrast, sharpening, and more when converting sensor data into a JPEG. So “completely unedited” usually really means “submitted as captured by the camera,” not “free of all processing.”

In practice, contests that want no post-processing often require straight-from-camera JPEGs rather than edited exports from RAW files. That is usually their standard for compliance.

So yes, they may be able to detect many edited files, especially obvious ones, but metadata alone is not a perfect or absolute proof of every adjustment. What they can reliably enforce is whether the submitted file appears to be an in-camera original versus something re-saved or altered later.