BrickMissing is a free tool for LEGO builders. Track which parts you're missing from any of 17,000+ sets, see every set a part appears in, and check a set's "repair risk" before you buy second-hand: the share of its parts that are nearly impossible to source because they only ever existed in a handful of sets. Built on 1.1M inventory records; the repairability dataset is a free CC BY 4.0 download.
