I thought options were FIFO but I’m not so sure anymore. The other day I was trading options on C and saw some weird things happen when I would undercut the bid or ask (suddenly tons of options swarming in on the new bid or ask, and then suddenly dissappearing when I took mine out — usually always the same number).
Another thing — at the end of the day I notice really horrible fills on options that I’m monitoring. I’ve seen people pay 50% too much or getting a really bad price for a…