[1] It produces black, gelatinous basidiocarps (fruit bodies) and is a common, wood-rotting species throughout the Northern Hemisphere, typically growing on dead attached branches of broadleaf trees.

It was subsequently considered a synonym of Exidia glandulosa, until Donk revised species concepts in 1966 and placed it in synonymy with E. plana.

[5] Both Dillenius (1741) and Withering (1776) gave the English name for this species as "Witches' butter",[4] though this name has subsequently also been applied to other gelatinous fungi, including E. glandulosa and the yellow Tremella mesenterica.

Exidia nigricans forms dark sepia to blackish, rubbery-gelatinous fruit bodies that are button-shaped and 1–2 centimetres (1⁄2–3⁄4 inch) across.

[8] Non-gelatinous, black fruit bodies on wood occur in other genera, including Annulohypoxylon, Biscogniauxia, Camarops, and Hypoxylon.

[6] Exidia nigricans is a wood-rotting species, typically found on dead attached branches of a wide range of broadleaf trees.