What Is Seaport? OpenSea's New NFT Marketplace Protocol

OpenSea announced on Tuesday, Jun. 14, that it is officially moving its NFT marketplace over to its new Seaport protocol, which is expected to save users more than $450 million a year in total transaction fees.*

Seaport is an open-source, decentralized, and base layer web3 marketplace protocol built to help users safely and efficiently buy, sell, and trade NFTs.

Immediate improvements following the OpenSea migration are expected to include: lower gas costs, offers on entire collections, offers on multiple assets with a specific trait, the removal of the new user account initialization fee, and more user-friendly contract signatures.

The lower gas fees are estimated to save 35 percent for all transactions, according to OpenSea, which is equal to $460 million (or, 138,000 ETH) in total savings based on last year's marketplace data.* The removal of the setup fee could also save new users more than $100 million (or, 35,000 ETH) per year.* And collection and trait offers, which were previously impossible due to OpenSea's former marketplace protocol, make it easier for users to purchase the NFTs they want the most, saving them bid cancellation fees and failed transactions.

*Note: These numbers are based on total transactions and new users from last year's OpenSea data. ETH and NFTs are volatile assets and those numbers are expected to fluctuate. 

In addition to these new developments, Seaport is supposed to decrease the amount of time it takes OpenSea to build and release new features. And the most popular NFT marketplace already has a new features in its pipeline for release, including the ability to bulk list NFTs, purchasing multiple NFTs in a single transaction, sending real-time creator fees to multiple recipients, setting variable fees on-chain on a per-item basis with multiple payout addresses, and more. 

Seaport will change the way users interact with OpenSea. But it isn't just OpenSea that Seaport benefits. As an open-source, decentralized web3 protocol, the core smart contract has no contract owner, upgradeability, or other special privileges. Anyone building an NFT marketplace can use Seaport for faster, safer, and more efficient transactions and features. 

How Does the Seaport NFT Marketplace Protocol Work?

The major distinguishing difference between most NFT marketplace protocols and Seaport is its ability to allow offers and considerations that include payment tokens (cryptocurrencies like ETH, SOL, etc.) and asset tokens (NFTs like Bored Apes).

"Seaport takes a different approach: offerers can agree to supply a number of ETH / ERC 20 / ERC721 / ERC 1155 items - this is the 'offer,' OpenSea's explanation of Seaport reads. "In order for that offer to be accepted, a number of items must be received by the recipients indicated by the offerer - this is the 'consideration.'"

In layman's terms, Seaport opens up the possibility of trading any combination of NFTs and cryptocurrencies for other NFTs and cryptocurrencies. The days of offering 100 ETH for a Bored Ape Yacht Club (BAYC) NFT are over. Now, you can offer five Doodles NFTs, three Moonbirds NFTs, and six ETH, for example.

Seaport's improved EIP-712 signature payload makes this possible and clearly outlines what can be spent and received by the buyer and seller. And it allows users to fulfill multiple single item transfers at once.

"Seaport also supports the option to fulfill any number of listings at once through a set of 'fulfillments' - each fulfillment corresponds to a single item transfer and indicates a group of offer items that the submitter can match with corresponding consideration items," OpenSea writes. "As long as each consideration item on each listing is fully credited after all fulfillments have been applied, the offerers can leverage their coincidence of wants and complete their transfers."

This eliminates redundant transfers, according to OpenSea, which is the most gas-intensive component of the protocol, and allows for "novel and efficient transactions."

Seaport also introduces optional criteria specificity rather than tokenId specificity, which means that sellers and traders can offer up their NFTs in exchange for NFTs with specified collection-level or trait-level matches. If you'd trade your entire NFT portfolio for a Bored Ape with gold fur, you can make that offer to all gold fur Bored Ape NFT holders with Seaport.

Additionally, sellers can specify distinct start and end amounts for their NFT sales, which when added with a start and end time can create Dutch auctions and reverse Dutch auctions. 

Listings can now also support partial fills on offered items, which means that offerers looking to purchase three floor price Moonbirds can add 60 ETH to their offer and accept at 20 ETH intervals until the entire contract is fulfilled. 

"Offerers can combine partial fills with criteria-based items to create standing offers to buy or sell multiple NFTs that all share a given characteristic," OpenSea explains.

And finally, tipping has been added to the Seaport protocol. Tips must not be more than the original offer, but buyers can now include additional consideration items (either payment or asset tokens) that are given to the seller upon the completion of the fulfillment. 

"This allows alternative interfaces to include their own fees, and can be combined with zones to support listings with dynamic amounts and recipients, as well as other novel applications like on-chain English auctions," according to OpenSea.

TL;DR How Does Seaport Make OpenSea Better?

Seaport opens up a host of new opportunities for both the OpenSea NFT marketplace and NFT marketplaces in general. Here are some improvements it makes possible:

• Lower fees - Seaport lowers transaction and gas fees and removes the new user initialization fee
• Bulk transfers - Seaport allows for the buying and selling of multiple assets in a single transaction
• Trading - Seaport makes exchanging payment tokens and asset tokens possible, allowing for NFT for NFT and ETH + NFT for NFT transactions
• Specific Offers - Seaport lets users buy, sell, and trade NFTs with collection-level or trait-level specificity
• New Sale Formats - Seaport supports Dutch and English auctions
• Tipping - Seaport adds the possibility of additional consideration items (like ETH or NFTs), or "tips," to be given to the seller upon the completion of a purchase or trade.

Why Is Seaport Open Source?

Seaport was built to accelerate use cases and feature optimizations for OpenSea. But now, it will serve as the primary base layer protocol for NFT marketplaces in the web3 space.

"We built the initial version of the protocol to unlock use cases and optimizations that creators and collectors expect from a modern web3 marketplace," OpenSea said. "However, what we've really built is a foundation to empower the developer community to work together on this primitive."

As previously mentioned, OpenSea does not control the protocol's core smart contract and does not have special privileges on Seaport. The company is actively encouraging the web3 community to participate in the development and evolution of Seaport.

"We’ve included a reference implementation that replicates the functionality of the optimized contract without any assembly code to enhance readability," the team writes. "We highly recommend contrasting the two implementations to familiarize yourself with the code (or even as an educational resource!) and encourage you to review and ask questions directly on the GitHub project — ongoing community engagement and participation is critical to the ongoing security and evolution of the protocol."

The motivations for OpenSea's open-source NFT marketplace protocol are unknown. But it will help the entire web3 space build and develop better resources, tools, and features for buying, selling, and trading digital assets. And that's what matters most. 

Is Seaport Safe?

Seaport has been reviewed for security-related issues both early in its development phase by OpenZeppelin and later in its development phase by Trail of Bits. The full report from Trail of Bits is available here.

Seaport is also offering a two-week audit contest with code4rena with a $1 million prize pool. Details on that audit contest are available here.