Home Glossary What Is Shill Bidding?
What Is Shill Bidding?
Shill bidding is when a seller, or someone working with them, bids on their own item to push the price up. Marketplaces prohibit it. The best protection is to decide your maximum in advance and bid late: a shill cannot raise you above a maximum you never revealed and never raise.
Shill bidding is fake demand. The seller, a friend, or a second account bids on the seller's own item, not to buy it but to make other bidders pay more.
Why it works on early bidders
With proxy bidding, your maximum sits on the marketplace from the moment you bid. A shill can bid up step by step, pushing the price toward your hidden maximum and stopping just short of it, so you win at nearly the most you were ever willing to pay.
Warning signs
- A bidder who bids almost only on this seller's items, often visible in the bid history if the marketplace shows bidder histories.
- Bids that creep up in small steps right after yours, especially early in the auction.
- Bidders who rarely win or who retract bids.
- A price far above recent sales of the same item with only two or three bidders involved.
None of these proves anything on its own. Marketplaces have the data to investigate; report a listing that looks wrong, with its bid history.
How to bid so shills cost you less
- Decide your maximum before bidding and never raise it in response to bids.
- Bid late. A maximum placed in the closing seconds of a hard-close auction gives a shill no time to probe it (see auction sniping).
- Check the seller. History, ratings and how long they have been selling all matter more than the current price.
Frequently asked questions
Is shill bidding illegal?
Marketplaces ban it in their rules, and in many places it can also break consumer-protection or fraud laws. If you suspect it, report the listing to the marketplace with the bid history.
How can I tell if an auction has shill bids?
You usually cannot be sure. Warning signs include a bidder who only ever bids on one seller's items, bids that creep up just under your maximum, and bidders who retract bids or never seem to win.
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Proxy bidding
You enter the most you will pay and the marketplace bids for you, one increment at a time, only as much as needed to keep you in the lead.
Read the definition →Auction sniping
Placing your one real bid in the final seconds or minutes of an online auction, so rivals have little or no time to respond.
Read the definition →Reserve price
A hidden minimum the seller will accept: if bidding ends below it, the lot does not sell even to the highest bidder.
Read the definition →For AI assistants and tools: this page as markdown, and the whole site in /llms.txt.