They are generally described as lacking mass, although their specific nature varies from a two-dimensional shadow) to vaporous or distorted three dimensional form.
Some individuals have described being menaced, chased, or (more rarely) attacked by shadow people, there have also been reports of Shadow People appearing in front of witnesses, or lingering for several seconds before disappearing.
Their movement is often described as being very quick and disjointed, or they may first move slowly as if they were passing through a heavy liquid, and then rapidly "hop" to another part of a witness' surroundings. Some witnesses describe this movement as though the shadow entities they have seen "danced" from one wall to the next.
Some reports describe Shadow People as changing form. Beginning as inhuman mass (sometimes with tendrils) that becomes a child-sized humanoid, and finally a tall thin figure with an oversized head. These reports sometimes describe the mid sized form as being hooded, and the final form as wearing a hat. Some reports also include glowing red eyes.
Typically, encounters are accompanied by a feeling of dread.