H. sanguineus has a squarish carapace, 2 inches (50 mm) in width, with three teeth along the forward sides; its pereiopods are marked with alternating light and dark bands.

As crab density in an invaded area increases, so does the breadth of the species' diet, which suggests that competition alters selection of food.

[6] The invasion of the habitat by the H. sanguineus has been characterized by rapid geographical expansion and widespread displacement of competing crab species.

On the other hand, native crabs also have adapted to eat H. sanguineus, possibly due to the availability of the food source or as an anti-predator strategy.

[11] There is a possibility that H. sanguineus could expand in numbers in some areas where it is invasive, potentially overwhelming the habitat and out-competing native crustaceans, such as the blue crab and lobster.

The native distribution of H. sanguineus is in coastal waters of the northwestern Pacific Ocean, ranging from Peter the Great Bay in southern Russia, to Hong Kong.

[12] The first record of this crab outside its native range[13][14][15] was from Townsends Inlet, Cape May County, New Jersey (between Avalon and Sea Isle City) in 1988.

[8] From the 1990s, it spread as an invasive species through similar vectors such as ballast water and became increasingly common, now ranging from eastern Maine (Great Wass Island)[17] to North Carolina.

[23] In 2019, Swedish authorities reported that a private person collected more than 50 specimens of the crab in the vicinity of the island of Orust in the Skagerrak–Kattegat region.