It is small, with an oval dark brown to black cephalothorax and a thinner ovoid abdomen that are each between 2.2 and 2.6 mm (0.09 and 0.10 in) in length.

The abdomen has thin white stripes along its middle and sides, which helps differentiate it from the related Evarcha flagellaris that also lives in the same area of the world.

[5] In Wayne Maddison's 2015 study of spider phylogenetic classification, the genus Evarcha was moved to the subtribe Plexippina.

[11] Evarcha karas is a small spider, similar in shape to others in the genus, with a body divided into two main parts: an oval cephalothorax and an ovoid abdomen.

The hard upper part of the cephalothorax, or carapace, is high and dark brown to black, covered in greyish-white or white hairs.

The spider's face, or clypeus, is moderately high and brownish with a covering of white hairs to the base.

The chelicerae also feature white hairs, while the remainder of the mouthparts, including the labium and maxillae, are brown.

In the same way as the carapace, the underside differs between geographies, with the South African spiders being blackish while those from Namibia are light with a hint of grey.

The long palpal tibia has a relatively large and prominent upward-pointing spike, or tibial apophysis, which has an end that finishes in two small similarly-sized points, one of which looks like a tooth.

[14] Evarcha spiders live across the world, although those found in North America may be accidental migrants.