OpenSea

OpenSea is the largest NFT marketplace by cumulative volume, having facilitated over $35 billion in trades since launching in 2017. It supports NFTs across ten major blockchains — including Ethereum, Solana, Polygon, Arbitrum, Optimism, Base, BNB, Avalanche, Flow, and Klaytn — and remains the default marketplace for most collectors entering the space. However, its market dominance has eroded significantly since 2023: Blur now commands the majority of daily trading volume on Ethereum, driven by its pro-trader interface, aggressive airdrop incentives, and lower fee structure. As of late 2025, OpenSea typically ranks second on Ethereum-based trading volume and remains the category leader on Polygon, Solana, and long-tail collections.

The platform charges a 2.5% transaction fee on secondary sales — recently reduced from earlier higher-fee iterations in an attempt to stay competitive with Blur's zero-fee model. Creators can set royalty rates between 0–10%, though enforcement has become inconsistent across the NFT industry; OpenSea currently honors creator royalties only on collections that enforce royalty contracts on-chain. In February 2024, OpenSea received an SEC Wells Notice indicating the agency's intent to pursue enforcement action against the company, alleging that NFTs sold on the platform constitute unregistered securities. The matter remains ongoing and introduces meaningful regulatory uncertainty for the entire NFT market, not just OpenSea.