OpenSea

OpenSea is an online marketplace where users buy, sell, list and create non-fungible tokens, including digital art, collectibles, gaming items and domain names. It was one of the first general-purpose NFT marketplaces and became the largest by trading volume during the 2021 boom. It supports Ethereum and several other networks, including Polygon, and users connect a self-custody wallet such as MetaMask to trade.

OpenSea is operated by Ozone Networks, a company based in New York that was founded in 2017 by Devin Finzer and Alex Atallah. It earns most of its revenue from a fee on each sale. Unlike curated platforms such as Nifty Gateway, it lets almost anyone list a collection, which made it central to the NFT market but also exposed it to fakes, stolen items and spam.

OpenSea works a lot like an online auction and classifieds site, but for digital items whose ownership is recorded on a blockchain. Sellers post an item with a fixed price or invite offers, and buyers browse by collection, price or popularity. When a sale happens, the token moves from the seller's wallet to the buyer's, and the payment moves the other way.

The important difference from a normal shop is that OpenSea does not usually hold the items. They stay in users' own wallets until a sale is settled on the chain. OpenSea provides the shop window, the search and the matching of orders, while the blockchain records who owns what.

OpenSea launched in the period when the first popular NFT collections, such as CryptoKitties, were appearing on Ethereum. Trading was modest until 2021, when demand for digital art and avatar collections surged and monthly volumes on the platform rose into the billions of dollars. In January 2022 the company announced a funding round that valued it at about 13.3 billion dollars. Volumes then fell sharply as the NFT market cooled during the crypto winter of 2022 and 2023, and the company cut staff. OpenSea also faced growing competition from marketplaces that charged lower fees or offered token rewards to traders.

• Listings and offers. Sellers sign an off-chain message that authorises a sale at a given price. The order is stored by OpenSea and executed on-chain only when a buyer accepts, which saves sellers from paying a network fee just to list.
• Seaport protocol. Since 2022, trades have been settled through Seaport, an open-source marketplace protocol that OpenSea released for others to use as well.
• Minting tools. Creators can deploy collections and set up primary sales, or "drops", through the platform.
• Fees. OpenSea charges a platform fee on each sale. Creator royalties may be added on top, although OpenSea made them optional for many collections from 2023.

Buyers pay the network's gas fee when settling a purchase on Ethereum, which can be significant during busy periods.

In 2022, a former OpenSea product manager was charged in the US with wire fraud and money laundering for buying NFTs shortly before they were featured on the site's homepage and selling them after prices rose, conduct prosecutors compared to insider trading. He was convicted in 2023, and an appeals court later overturned the conviction. The platform has also struggled with stolen NFTs, copied collections and wash trading designed to inflate volumes or farm rewards on rival venues, and it introduced systems to flag suspicious items. Users have lost NFTs through phishing sites that imitate OpenSea and trick them into signing malicious approvals.

In August 2024 OpenSea said it had received a Wells notice from the US Securities and Exchange Commission, indicating the agency was considering action on the theory that some NFTs traded on the platform were securities. In early 2025 the company said the SEC had closed the investigation without taking action.

OpenSea helped establish many of the practices that now define NFT trading, including off-chain order books, collection pages, verified-collection badges and creator fee settings. Its dominance did not last unchallenged. From late 2022, Blur, a marketplace aimed at professional traders, won a large share of Ethereum NFT volume by offering zero platform fees, faster tools and token rewards for active trading, and Magic Eden grew from its base on Solana to other chains. Competition pushed fees down across the market and contributed to the weakening of creator royalties.

NFT trading activity has stayed well below its 2021 peak since the downturn of 2022. OpenSea has responded by redesigning its platform and adding features for trading fungible tokens as well as NFTs, in an effort to broaden its role beyond a single asset class. Like other marketplaces, it also has to manage legal questions over intellectual property, sanctions screening and consumer protection, since the items it lists are created by third parties it does not vet in advance.

• OpenSea