Technical Definition
Post-Only Order
A limit order flag that ensures the order only adds liquidity to the order book (acts as maker) and is canceled/rejected if it would immediately match/take existing orders.
By Crypto University Editorial
Maker FeeLimit OrderIOC/FOK
✦ Key Insight
Why It Matters: Guarantees maker fees (often lower or rebates) instead of taker fees; ideal for cost optimization and providing liquidity without accidental aggressive fills. How It Works: When placing a limit order, enable "Post-Only." If the price would cross the book immediately, the order is
✕ Common Misconceptions
It is often mistaken for similar sounding terms, but the technical implementation is distinct.
Detailed Explanation
Why It Matters:
Guarantees maker fees (often lower or rebates) instead of taker fees; ideal for cost optimization and providing liquidity without accidental aggressive fills.
How It Works:
When placing a limit order, enable "Post-Only." If the price would cross the book immediately, the order is rejected instead of executing as taker.
Common Mistakes:
Forgetting to enable it and paying higher taker fees; placing too aggressively and getting rejected repeatedly.
FAQs
Why use it?
To avoid taker fees and potentially earn rebates on high-volume tiers.
Available everywhere?
Most major CEX futures/spot support it.
In Practice
“On Bybit or Binance, set a buy limit at $59,800 for BTC when current ask is $59,900 — it posts safely; if market drops instantly, it's rejected rather than taking.”