Encyclopedia Ethereum · Entry 249
NFT listings and offers: how signatures become marketplace trades
In this article
At a glance
Key facts
| Fact | Detail | Source |
|---|---|---|
| Offer | A Seaport order identifies items the offerer will supply. | [1] |
| Consideration | It also identifies required items and their recipients. | [1] |
| Fulfillment | Valid signatures, time bounds, balances and approvals affect executability. | [1] |
An order and an approval do different work
A token approval allows the relevant contract or conduit to move tokens. The order specifies the exchange that Seaport may perform using those permissions. Signing a sale message therefore can be materially different from signing a simple login.
Read the asset, token ID or criteria, currency, recipients and time window. Some orders cover any eligible token in a set rather than one specific item.
A signed sale can be filled later
Suppose a seller signs an order offering one NFT for 1 ETH before a stated expiry and has granted the necessary transfer approval. A buyer can later fulfill the still-valid order by supplying its required consideration. The seller need not be online to press another approval button.
If the seller changes their mind, merely closing the page does not cancel that signed authorization. Seaport documents individual cancellation and counter-based invalidation mechanisms.
Use the protocol’s cancellation state
An offchain website can stop showing an order without making the underlying signed order unexecutable elsewhere. Where cancellation is required, follow the protocol-supported onchain method and verify the resulting state.
An expired, cancelled, already filled or insufficiently approved order may fail fulfillment. A listing displayed in an interface is not proof it can still be bought. This example concerns documented Seaport behavior, not every marketplace protocol.
Direct answers
Questions people ask
Does signing a listing immediately transfer the NFT?
Not necessarily. A signed order can authorize future fulfillment. The actual transfer occurs when an executable order is fulfilled onchain.
Does removing a listing from a website always cancel its signature?
No. Interface removal and protocol cancellation are different. Check the order’s actual cancellation, counter and expiry conditions.
Inspect the evidence
The answer and key facts have stable claim links. These records retain the scope and qualification when reused.
An NFT listing or offer can be a signed order that becomes executable later when its conditions, balances and approvals are satisfied. In Seaport, the order specifies offered items, required consideration, recipients and validity times. Signing it is different from granting token approval, but both can combine to enable a sale without another signature from the seller.
Scope: Ethereum · data through 2026-10-02. Verification: verified · 2026-10-02T19:27:58.939Z.
Link to this claimOffer: A Seaport order identifies items the offerer will supply.
Scope: Ethereum · data through 2026-10-02. Verification: verified · 2026-10-02T19:27:58.939Z.
Link to this claimConsideration: It also identifies required items and their recipients.
Scope: Ethereum · data through 2026-10-02. Verification: verified · 2026-10-02T19:27:58.939Z.
Link to this claimFulfillment: Valid signatures, time bounds, balances and approvals affect executability.
Scope: Ethereum · data through 2026-10-02. Verification: verified · 2026-10-02T19:27:58.939Z.
Link to this claimRevision history
- — First publication after primary-source research and separate automated verification.
Source register
Sources and references
Retrieval dates and locators are recorded individually.- Seaport order and fulfillment documentationOpenSea contributors
Offer/consideration orders, signed authorization, approval and order fulfillment.
Locator: Orders; fulfillment; cancellation; signatures · Version / scope: Seaport repository documentation; retrieved content hash recorded · Retrieved: 2026-10-02T18:58:48.251ZOpen source
Research and drafting use AI assistance. A separate automated review checks claims against primary sources; no external expert or named human review is implied. Publication, substantive editing, source retrieval and verification are recorded separately. This version was independently checked by an automated reviewer on 2 October 2026.
Editorial method and correctionsDegrees of Satoshi editorial project. “NFT listings and offers: how signatures become marketplace trades.” Published 2026-10-02; updated 2026-10-02. https://degreesofsatoshi.com/encyclopedia/nft-listings-and-offers/