Planaxidae, commonly called planaxids or clusterwinks, are a taxonomic family of small and minute sea snails, pantropical marine gastropod molluscs in the superfamily Cerithioidea.

They live on rocky shores in the littoral zone of the tropics and subtropics.

[2] Planaxids are known as clusterwinks because of their habit of clustering together in concealed, moist locations when the tide is out.

They have conical shells resembling periwinkles, except for the wide, shallow anterior canals.

They brood their embryos in a chamber behind their heads, releasing them into the sea as veliger larvae to form part of the plankton.