BriX is a vast database of protein fragments, clustered on their backbone similarity. BriX contains fragments from 7290 proteins from the Astral40 set, fragmented in lengths ranging from 4 to 14 amino acids and clustered against 6 different distance thresholds on similarity of the protein backbone. Loop BriX contains loop fragments from 14.525 proteins from the Astral95 set, clustered according to end-to-distance and anchor residue superposition.