{
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  "id": "post-only-orders",
  "canonical": "https://degreesofsatoshi.com/encyclopedia/post-only-orders/",
  "collection": "defi",
  "title": "Post-only orders: requiring a maker order instead of an immediate fill",
  "description": "Explain why a maker-only order can be rejected, and why resting successfully does not guarantee a trade.",
  "aliases": [
    "post only order rejected",
    "why was my post only order cancelled"
  ],
  "dates": {
    "published": "2026-10-02",
    "modified": "2026-10-02",
    "verified": "2026-10-02T19:18:00.092Z",
    "dataAsOf": "2026-10-02"
  },
  "authorship": {
    "publisher": "Degrees of Satoshi editorial project",
    "process": "AI-assisted research and drafting with a separate automated source-verification pass; no external expert or named human review is implied."
  },
  "quickAnswer": {
    "text": "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.",
    "claimId": "post-only-orders-quick-answer",
    "sourceIds": [
      "x425-defi-dydx-orders"
    ]
  },
  "keyFacts": [
    {
      "label": "Maker intent",
      "value": "The order should rest on the book.",
      "sourceIds": [
        "x425-defi-dydx-orders"
      ],
      "id": "maker-intent",
      "claimId": "post-only-orders-fact-maker-intent"
    },
    {
      "label": "Crossing",
      "value": "A dYdX post-only order is cancelled if it immediately matches an existing order.",
      "sourceIds": [
        "x425-defi-dydx-orders"
      ],
      "id": "crossing",
      "claimId": "post-only-orders-fact-crossing"
    },
    {
      "label": "Separate price",
      "value": "The limit price still bounds acceptable execution.",
      "sourceIds": [
        "x425-defi-dydx-orders"
      ],
      "id": "separate-price",
      "claimId": "post-only-orders-fact-separate-price"
    }
  ],
  "prerequisites": [
    "order-book-depth-spread"
  ],
  "sections": [
    {
      "id": "example",
      "heading": "A competitive price can conflict with maker-only status",
      "sourceIds": [
        "x425-defi-dydx-orders"
      ],
      "paragraphs": [
        "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."
      ]
    },
    {
      "id": "fees",
      "heading": "Maker classification is not a return promise",
      "sourceIds": [
        "x425-defi-dydx-orders"
      ],
      "paragraphs": [
        "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."
      ]
    },
    {
      "id": "other",
      "heading": "Check other constraints separately",
      "sourceIds": [
        "x425-defi-dydx-orders",
        "x425-defi-dydx-reduce"
      ],
      "paragraphs": [
        "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."
      ]
    }
  ],
  "faq": [
    {
      "question": "If a post-only order disappears, did it necessarily trade?",
      "answer": "No. It may have been cancelled for crossing the book, expired or been cancelled for another reason. Check the filled quantity and execution history.",
      "sourceIds": [
        "x425-defi-dydx-orders",
        "x425-defi-dydx-screen"
      ]
    }
  ],
  "claims": [
    {
      "id": "post-only-orders-quick-answer",
      "articleSlug": "post-only-orders",
      "statement": "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.",
      "sourceIds": [
        "source-a2545baf2d42e7b4"
      ],
      "sourceLocators": [
        {
          "sourceId": "source-a2545baf2d42e7b4",
          "locator": "Market; Limit; Stop; Take Profit; execution policies"
        }
      ],
      "scope": {
        "collection": "defi",
        "dataAsOf": "2026-10-02",
        "blockHeight": null
      },
      "qualification": "",
      "evidenceStatus": "documented",
      "verification": {
        "status": "verified",
        "method": "independent automated source review",
        "checkedAt": "2026-10-02T19:18:00.092Z",
        "reviewer": "Independent automated verification — Codex root, separate from the DeFi drafting agent",
        "notes": [
          "Checked dYdX post-only rejection when matching and current reduce-only IOC restriction; maker classification does not promise zero/negative fees."
        ]
      }
    },
    {
      "id": "post-only-orders-fact-maker-intent",
      "articleSlug": "post-only-orders",
      "statement": "Maker intent: The order should rest on the book.",
      "sourceIds": [
        "source-a2545baf2d42e7b4"
      ],
      "sourceLocators": [
        {
          "sourceId": "source-a2545baf2d42e7b4",
          "locator": "Market; Limit; Stop; Take Profit; execution policies"
        }
      ],
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        "checkedAt": "2026-10-02T19:18:00.092Z",
        "reviewer": "Independent automated verification — Codex root, separate from the DeFi drafting agent",
        "notes": [
          "Checked dYdX post-only rejection when matching and current reduce-only IOC restriction; maker classification does not promise zero/negative fees."
        ]
      }
    },
    {
      "id": "post-only-orders-fact-crossing",
      "articleSlug": "post-only-orders",
      "statement": "Crossing: A dYdX post-only order is cancelled if it immediately matches an existing order.",
      "sourceIds": [
        "source-a2545baf2d42e7b4"
      ],
      "sourceLocators": [
        {
          "sourceId": "source-a2545baf2d42e7b4",
          "locator": "Market; Limit; Stop; Take Profit; execution policies"
        }
      ],
      "scope": {
        "collection": "defi",
        "dataAsOf": "2026-10-02",
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      "evidenceStatus": "documented",
      "verification": {
        "status": "verified",
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        "checkedAt": "2026-10-02T19:18:00.092Z",
        "reviewer": "Independent automated verification — Codex root, separate from the DeFi drafting agent",
        "notes": [
          "Checked dYdX post-only rejection when matching and current reduce-only IOC restriction; maker classification does not promise zero/negative fees."
        ]
      }
    },
    {
      "id": "post-only-orders-fact-separate-price",
      "articleSlug": "post-only-orders",
      "statement": "Separate price: The limit price still bounds acceptable execution.",
      "sourceIds": [
        "source-a2545baf2d42e7b4"
      ],
      "sourceLocators": [
        {
          "sourceId": "source-a2545baf2d42e7b4",
          "locator": "Market; Limit; Stop; Take Profit; execution policies"
        }
      ],
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        "collection": "defi",
        "dataAsOf": "2026-10-02",
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      "evidenceStatus": "documented",
      "verification": {
        "status": "verified",
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        "checkedAt": "2026-10-02T19:18:00.092Z",
        "reviewer": "Independent automated verification — Codex root, separate from the DeFi drafting agent",
        "notes": [
          "Checked dYdX post-only rejection when matching and current reduce-only IOC restriction; maker classification does not promise zero/negative fees."
        ]
      }
    }
  ],
  "sources": [
    {
      "id": "x425-defi-dydx-orders",
      "label": "Perpetual order types on dYdX Chain",
      "publisher": "dYdX Operations Services",
      "url": "https://help.dydx.trade/en/articles/166981-perpetual-order-types-on-dydx-chain",
      "locator": "Market; Limit; Stop; Take Profit; execution policies",
      "note": "Order-type semantics and dYdX-specific constraints.",
      "version": "Documentation retrieved for the 2026-10-02 editorial scope; content hash recorded",
      "checkedAt": "2026-10-02T18:53:20.714Z",
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      "recordId": "source-a2545baf2d42e7b4"
    },
    {
      "id": "x425-defi-dydx-reduce",
      "label": "Reduce Only Order",
      "publisher": "dYdX Operations Services",
      "url": "https://help.dydx.trade/en/articles/166978-reduce-only-order",
      "locator": "Requirements; How it works",
      "note": "Version-scoped IOC requirement and reduction behavior.",
      "version": "Documentation retrieved for the 2026-10-02 editorial scope; content hash recorded",
      "checkedAt": "2026-10-02T18:53:20.744Z",
      "contentSha256": "a4a5a389c7a91e92510cd780bdeaa3d4278528624e099955953b21250b68bfe1",
      "recordId": "source-c3db43b5e8f8e4aa"
    },
    {
      "id": "x425-defi-dydx-screen",
      "label": "Interface of the Trade tab",
      "publisher": "dYdX Operations Services",
      "url": "https://help.dydx.trade/en/articles/166979-interface-of-the-trade-tab",
      "locator": "Orderbook; Position information; Stats",
      "note": "Definition and presentation of trading market metrics.",
      "version": "Documentation retrieved for the 2026-10-02 editorial scope; content hash recorded",
      "checkedAt": "2026-10-02T18:53:20.712Z",
      "contentSha256": "2548899a309c289e661f6f554a87ca26b9889d83ae3ac3cb9035ef8af84c7063",
      "recordId": "source-08e71d7fe0f46d5d"
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  ],
  "related": {
    "articles": [
      "order-time-in-force",
      "reduce-only-orders",
      "limit-orders-onchain"
    ],
    "dossiers": [],
    "wallets": []
  },
  "revisionHistory": [
    {
      "date": "2026-10-02",
      "kind": "published",
      "summary": "First publication after primary-source research and separate automated verification."
    }
  ],
  "citation": "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/"
}