Updated: 2026-02-20
In trading, Post-only order is an order that must add liquidity; it will cancel if it would immediately execute as a taker. This glossary entry explains why post-only order matters, how traders use it, and how to track it with evidence instead of vibes.
Quick definition
Post-only order: an order that must add liquidity; it will cancel if it would immediately execute as a taker.
Post-only order is an order that must add liquidity; it will cancel if it would immediately execute as a taker. The practical version is: can you define it as a field you can log and audit later?
Most trading terms become confusing when they are used as vibes instead of variables. Your goal is a definition that helps you decide size, stop, entry timing, or whether to skip the trade.
Traders sometimes confuse Post-only order with limit order. Treat them as separate variables in your journal so your reviews stay honest.
Post-only is a fee and execution control tool. It helps you avoid taker fees, but it can increase missed fills if price moves quickly.
If Post-only order never changes your decision, it is just jargon. The term earns its place when it improves your process consistency under real market pressure.
A useful mental model: plan first (risk and invalidation), execute second (order type and fills), review last (tags and metrics).
Use it to make one decision pre-trade. Example decisions: where the stop goes, whether to take partials, how to scale size, or whether conditions are too thin to trade.
Write the rule in one sentence, then run it consistently for a week. Consistency matters because it creates comparable data for review.
If the rule fails, adjust slowly. Do not rewrite the whole system after one bad session.
Record how often post-only orders cancel and how often you re-enter with worse price. If cancel rate is high, the instrument may not suit maker-style execution.
Use tags so you can slice results by regime and behavior state. The same term behaves differently when volatility changes or when you are fatigued.
Your review question should be binary: did this variable improve outcomes or reduce rule breaks? If not, simplify.
You place a post-only sell at 110, but price is 110.01 and would instantly fill. The exchange cancels your order instead, so you remain exposed.
The point of an example is not to predict price. It is to show what you would log before the trade and what you would audit after the trade.
Using post-only for urgent exits, where fill certainty matters more than saving a few bps.
The fastest way to improve post-only order is to remove one failure mode at a time. If you try to fix everything, you will fix nothing.
Post-only order matters most when volatility is high and the book is thin. That's where small execution errors compound into expectancy drag.
Before you trade, decide what matters more: price control (limits) or fill certainty (markets/stops). Then trade the choice consistently for one week so your data is comparable.
If you change order types every time you feel stressed, your metrics will lie to you.
Post-only order is an order that must add liquidity; it will cancel if it would immediately execute as a taker. In practice, it matters when it changes a concrete decision like size, stop placement, or whether you skip a trade.
They are related but not identical. In your journal, track Post-only order as its own variable and treat limit order as a separate context factor so you can audit each cleanly.
Record how often post-only orders cancel and how often you re-enter with worse price. If cancel rate is high, the instrument may not suit maker-style execution.
Using post-only for urgent exits, where fill certainty matters more than saving a few bps.
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