I build SIGNUM HQ, a free app that shows options positioning for US equities: open interest by strike, gamma exposure and the flip level, max pain, IV skew, and off-exchange volume share computed from FINRA's own published data. Each ticker is ranked against its own 30-day baseline rather than by absolute size, so the list is not just the same five mega caps every day.Free and ad supported. Nothing is paywalled - the one subscription removes ads and unlocks no data. English, Korean and Japanese.
https://www.signumhq.com/app?from=hn
Happy to talk about where the data comes from or how the calculations are done.