Shill bidding simulator

What’s happening

eBay keeps your maximum private and bids for you, one increment at a time, whenever someone outbids you. A shill can’t see your maximum, but they can find it: each small bid they place makes eBay raise yours one step, until they stop just short of it. You still win, at close to the most you were willing to pay.

The highlighted rows show the trace this leaves: one bidder placing small bids again and again, each answered straight away by the leader’s automatic bid. That staircase is what Susbid’s small consecutive bids sign looks for in a real bid history. Many cautious buyers bid the same way, which is why the report shows that innocent explanation beside it.

Why bidding late changes the result

Switch to “Late” and your maximum isn’t in the auction while the shill is bidding. The shill can only push against the bidders it can see, and stops once it leads, because leading means it might win. When you bid at the end, you pay one increment over that, not close to your maximum.

Bidding late, often with a sniping tool, has trade-offs: you can miss the end, and eBay is testing extended bidding in some categories, where a bid in the final seconds adds time. Deciding your real maximum before you bid protects you either way: a shill can never push you past it.

What the simulator leaves out

Real auctions have more bidders, shills can use several accounts or retract bids, and bidders show as masked names with feedback scores. This is a teaching model with made-up bidders, not a detector. To look at a real auction, use the checker.

Common questions