# Post-only orders: requiring a maker order instead of an immediate fill A post-only order is intended to add resting liquidity rather than immediately match an existing order. In the documented dYdX behavior, an order that would match any existing quantity is cancelled instead of taking that liquidity. Post-only constrains execution style; it does not guarantee a future fill or a positive maker rebate. Evidence: [Perpetual order types on dYdX Chain](https://help.dydx.trade/en/articles/166981-perpetual-order-types-on-dydx-chain) Canonical: https://degreesofsatoshi.com/encyclopedia/post-only-orders/ Published: 2026-10-02 Substantively modified: 2026-10-02 Independently verified by an automated reviewer: 2026-10-02T19:18:00.092Z Data current through: 2026-10-02 AI-assisted research and drafting with a separate automated source-verification pass; no external expert or named human review is implied. ## Key facts - **Maker intent:** The order should rest on the book. ([Perpetual order types on dYdX Chain](https://help.dydx.trade/en/articles/166981-perpetual-order-types-on-dydx-chain)) - **Crossing:** A dYdX post-only order is cancelled if it immediately matches an existing order. ([Perpetual order types on dYdX Chain](https://help.dydx.trade/en/articles/166981-perpetual-order-types-on-dydx-chain)) - **Separate price:** The limit price still bounds acceptable execution. ([Perpetual order types on dYdX Chain](https://help.dydx.trade/en/articles/166981-perpetual-order-types-on-dydx-chain)) ## A competitive price can conflict with maker-only status Imagine the lowest ask is 100 B per A. A normal buy limit at 101 can immediately buy that ask. A post-only buy at 101 would cross the book, so under the documented rule it is cancelled rather than filled. A buy at 99 may rest, but another trader still needs to sell into it. The book can also move between a preview and submission. Evidence: [Perpetual order types on dYdX Chain](https://help.dydx.trade/en/articles/166981-perpetual-order-types-on-dydx-chain) ## Maker classification is not a return promise Post-only can prevent unintended taker execution under its specific rules. The actual maker fee or rebate depends on the venue and account schedule. A maker fill can still be followed by an adverse price move, so a favorable fee alone does not establish a profitable trade. Evidence: [Perpetual order types on dYdX Chain](https://help.dydx.trade/en/articles/166981-perpetual-order-types-on-dydx-chain) ## Check other constraints separately A resting order can have expiry and cancellation rules. Reduce-only is a different constraint on position exposure and is not automatically implied by post-only. In the cited dYdX guide, reduce-only requires IOC, illustrating why not every combination of familiar order flags is valid. Evidence: [Perpetual order types on dYdX Chain](https://help.dydx.trade/en/articles/166981-perpetual-order-types-on-dydx-chain); [Reduce Only Order](https://help.dydx.trade/en/articles/166978-reduce-only-order) ## Questions ### If a post-only order disappears, did it necessarily trade? No. It may have been cancelled for crossing the book, expired or been cancelled for another reason. Check the filled quantity and execution history. Evidence: [Perpetual order types on dYdX Chain](https://help.dydx.trade/en/articles/166981-perpetual-order-types-on-dydx-chain); [Interface of the Trade tab](https://help.dydx.trade/en/articles/166979-interface-of-the-trade-tab) ## Claims and scope ### post-only-orders-quick-answer A post-only order is intended to add resting liquidity rather than immediately match an existing order. In the documented dYdX behavior, an order that would match any existing quantity is cancelled instead of taking that liquidity. Post-only constrains execution style; it does not guarantee a future fill or a positive maker rebate. Scope: {"collection":"defi","dataAsOf":"2026-10-02","blockHeight":null} ### post-only-orders-fact-maker-intent Maker intent: The order should rest on the book. Scope: {"collection":"defi","dataAsOf":"2026-10-02","blockHeight":null} ### post-only-orders-fact-crossing Crossing: A dYdX post-only order is cancelled if it immediately matches an existing order. Scope: {"collection":"defi","dataAsOf":"2026-10-02","blockHeight":null} ### post-only-orders-fact-separate-price Separate price: The limit price still bounds acceptable execution. Scope: {"collection":"defi","dataAsOf":"2026-10-02","blockHeight":null} ## Sources - [Perpetual order types on dYdX Chain](https://help.dydx.trade/en/articles/166981-perpetual-order-types-on-dydx-chain) — dYdX Operations Services. Order-type semantics and dYdX-specific constraints. Locator: Market; Limit; Stop; Take Profit; execution policies. Retrieved: 2026-10-02T18:53:20.714Z. - [Reduce Only Order](https://help.dydx.trade/en/articles/166978-reduce-only-order) — dYdX Operations Services. Version-scoped IOC requirement and reduction behavior. Locator: Requirements; How it works. Retrieved: 2026-10-02T18:53:20.744Z. - [Interface of the Trade tab](https://help.dydx.trade/en/articles/166979-interface-of-the-trade-tab) — dYdX Operations Services. Definition and presentation of trading market metrics. Locator: Orderbook; Position information; Stats. Retrieved: 2026-10-02T18:53:20.712Z. ## Revision history - 2026-10-02: First publication after primary-source research and separate automated verification. ## Cite this entry Degrees of Satoshi editorial project. “Post-only orders: requiring a maker order instead of an immediate fill.” Published 2026-10-02; updated 2026-10-02. https://degreesofsatoshi.com/encyclopedia/post-only-orders/