Wingspan 4-5 mm.
Fairly common in mainland Britain, this species has an extended generation with adults flying from May to July and larval mines being found between August and November.
The foodplant is birch (Betula spp.), and the larva forms a gallery mine, initially highly contorted, later becoming straighter, usually with irregular blackish frass.
The adult moth is narrow-winged with a purplish-bronzy sheen. There is a whitish fascia which narrows towards the costa, outside which the purple colour is darker.