Woodsia ilvensis is a small fern that usually grows on rocks. The fronds are less than 25 cm long and 3.5 cm wide and grow in clumps. The blade is usually twice pinnate, at least at the base, and the abaxial (lower) surface bears conspicuous hairs and scales. The veins end short of the margin in a raised "hydathode", best seen on the adaxial (upper) surface of the segments. The stipe (sometimes referred to as "jointed") breaks off at an abcission layer, leaving a conspicuous persistent base that is useful in distinguishing this species.

W. ilvensis is known from Newfoundland and the farthest northern portions of Quebec and Yukon to Virginia, Ohio and Minnesota. It is also found in the west from Alaska to British Columbia and Alberta. It is widely distributed in Wisconsin, but absent in the eastern counties and in the mid-northern region. Even in the areas for which it is known it is often very local.