Post-only order
Post-only is a limit order setting that only lets the order enter the book as a maker. If it would fill immediately, the exchange cancels it, so you never pay the taker fee.
How it works
A maker adds liquidity to the order book (the order waits for someone to match it); a taker removes liquidity by filling at once. Maker fees are usually lower, and on some venues zero or even negative. Post-only guarantees you are the maker.
If you place a limit buy above the best ask, a normal limit order fills instantly as a taker. A post-only order in that case is cancelled instead (some exchanges reprice it to the nearest maker price). It never partly fills as a taker.
Post-only is used by active traders, grid bots and market makers, for whom the fee difference across thousands of trades adds up. The downside is that in a fast market orders may keep getting cancelled and you can miss the trade.
The best BTC ask is $60,010 and the best bid is $60,000. You place a post-only buy at $60,005: it rests in the book and waits for a seller. A post-only buy at $60,020 would cross the ask and fill at once, so the exchange cancels it.
On $200,000 of monthly volume, a 0.05% taker fee versus a 0.02% maker fee is $100 versus $40, so $60 saved.
Beginners switch on post-only, see the order vanish and assume it is a bug. It is not: the order would have filled immediately, so it was cancelled. If getting into the trade matters more than saving on fees, use a normal limit or market order.
Questions and answers
What is a post-only order in simple terms?
It is a checkbox on a limit order that means maker only. The order either rests in the book and waits or gets cancelled, but it never fills instantly against someone else's price.
Why was my post-only order cancelled?
Your price crossed the best opposite price, so the order would have filled at once as a taker. Set the price a little further from the market.
Why use post-only instead of a normal limit order?
A normal limit order can fill instantly and pay the taker fee. Post-only guarantees the maker fee, which matters when you trade often.
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Updated: 2026-10-19