What is the difference between an NFT contract and a collection?

"Contract" and "Collection" are terms used to describe two related but different types of groupings of NFTs. Their specific implementations vary across blockchain ecosystems.

• Contracts:
  On EVM-based chains, an NFT contract is a smart contract (typically following the ERC-721 or 1155 standards) responsible for issuing NFTs. Each contract has a unique on-chain address, such as 0x524cAB2ec69124574082676e6F654a18df49A048 for Lil Pudgys. NFTs adhering to the 721 or 1155 standards can always be identified by their contract address and individual token ID. Contracts remain consistent on-chain regardless of the marketplace or protocol interacting with the NFT.
• Collections:
  On EVM-based chains, NFT collections are often tied to a specific marketplace and represented off-chain, with unique identifiers such as proof-moonbirds on OpenSea. Collections may be represented differently across various marketplaces and protocols. While contracts and collections are often 1:1, there are exceptions, such as the OpenSea storefront contract, which contains multiple individual collections.

The relationship between contract and collection can be like this:

How to Trade with Blur Orders?

Trading with Blur Orders is distinct from other orders due to its unique mechanism and workflow. Blur Orders necessitate that the EOA signs an authentication message just once for all subsequent trading operations.

To incorporate the Blur Order trading feature into your product, it's essential to integrate both the GetBlurAuthChange API and GetBlurAuth API. After this integration, you should pass the blur auth to the extra_args parameter of the NFT trading APIs.

To obtain the EOA's blur auth, please follow the instructions below.

Note: You can use https://web3js.readthedocs.io/en/v1.2.11/web3-eth-personal.html#sign to let EOA sign the message.

Why can't I collect marketplace fees in addition to Blur Orders?

In order to collect marketplace fees, our system utilizes the aggregator contract. During the order fulfillment process, the transaction is first directed to the aggregator contract, which then calls upon the corresponding marketplace contract to complete the order fulfillment.

However, there is a limitation with the Blur contract. It restricts any third-party aggregator contract from invoking it, with the exception for the Blur Aggregator Contract. This limitation hinders the functionality of collecting marketplace fees on top of Blur orders.