Bid on your favorite Crypto Collectibles!

Offer ETH for non-fungible tokens without paying gas* or fees

Today we’re launching a huge upgrade to our marketplace: the ability to bid with Ether on any crypto collectible, regardless of whether it’s on sale. We’re phasing out our escrow contract and replacing it with a wallet-to-wallet exchange 🔁. Here’s what this means for users:

For buyers:

See an item you want to buy but it’s priced too high, or not even on sale? You can now create an “offer” for this item, just like on eBay! When the seller goes to visit their account page, they’ll see your offer (plus they’ll get notified by email if they have an OpenSea account):

Collectibles now accept offers, a.k.a.“buy orders.” No need for the seller to put it on auction!

The best part: you can re-use the same Ether to bid on multiple items! That way you can make offers on your favorite kitties, sit back, and “race” sellers to fulfill one of them while you sleep.

Huge gas savings

All the bids live off-chain, but the settlement of these orders will happen on-chain. This means that the blockchain is only needed when a seller accepts an offer.

We heavily optimized our architecture to minimize your spend on gas. While there is some upfront gas required to initialize your account, once you’ve done that upfront transaction, all future bids will be instant and free!

For sellers:

This is also huge news for sellers! Remember how before, you always had to guess how to price your item and then wait a couple days to see whether you went too high or low? Now can easily advertise your item to buyers without having to figure out how to price your item. Perhaps you have a high “buy it now” price for which you’re immediately willing to sell, but you allow bids to climb up beneath it. As a matter of fact, all assets (on sale on OpenSea, on another platform, or not on sale at all) are biddable, so you can always view and accept offers at any time. You might have open offers now: see if you do.

Buyers can now “vote” on how valuable your items are

And here’s the best part for you: when an item is on sale, you can still use it in the game! For example, you can continue to battle Mythereum cards while you watch potential buyers bid on them. And all payments that go to the owner of the item will go to you, instead of being disabled or going nowhere, which is what unfortunately happens for auctions on other marketplaces.

No more escrow. Trade straight from wallet to wallet.

With most in-game crypto marketplaces, sellers will transfer an item into an “escrow contract” when they want to sell it. This was problematic because the item would live in a separate address while it was on sale, not fully under the user’s control. Additionally, to get it out of escrow, the user would have to complete another transaction to cancel the auction.

We got rid of escrow entirely. Now, when you put an item on sale, your item stays right in your wallet. This means you can still use it in the game, show it off in your OpenSea trophy case, or make it into a t-shirt. You simply post an off-chain sale, indicating that you’d like to sell this item.

Which items are supported?

Making offers on OpenSea works with almost all non-fungible tokens. Here are some of the Mainnet asset types that are currently supported, with more being added all the time:

  • CryptoKitties — the game that started it all. Breedable, collectible, and oh-so-adorable cats, each one-of-a-kind and owned by you. They cannot be replicated, taken away, or destroyed.
  • Decentraland — a virtual reality platform powered by the Ethereum blockchain. Users can create, experience, and monetize content and applications.
  • Crypto Space Commander — a space MMO that operates in a completely real-time, player-controlled economy.
  • CryptoStrikers — users can buy, sell, or trade soccer player cards like traditional collectibles, fully confident that the blockchain will track ownership securely.
  • Eth.Town — become a realtor buying out floors for certain crypto-companies in a crypto-business tower.
  • CryptoBots — a battling game centered around cryptographically unique collectible bots.
  • Cryptovoxels — a virtual world on the Ethereum blockchain. Build, develop and sell property. You own your own land, with your ownership recorded permanently on the blockchain.
  • Mythereum — a multiplayer digital trading card game built on the Ethereum blockchain where players build unique decks of collectible cards and challenge others to engage in battle.
  • CryptoFighters — cryptographically unique collectible fighters on the Ethereum blockchain. Collect, battle and level up your fighters to win new fighters!
  • CryptoMasterpieces — the first platform for collecting one-of-a-kind digital masterpieces. Collectors can buy, sell and trade famous artwork.
  • CryptoCrystal — sentient crystals that have personalities similar to humans while being cute like pet animals.
  • CryptoCelebrities — a popular game involving celebrity trading cards, which are still being traded and used in follow-up games.
  • CryptoRacing — race rare, collectible cars.
  • Cryptogs — Whip out your slammer and get rad on the blockchain! Born at ETHDenver, Cryptogs is the game of pogs on Ethereum.
  • DigitalArtChain — Publish your own digital art on the blockchain. Digital Art is published on IPFS, enabling you own, sell, and purchase published digital art.
  • John Orion Young — a contemporary artist living in San Francisco. Classically trained from childhood in his father’s art studio in painting and sculpting, JOY’s mediums today have evolved to include virtual reality, blockchain, and AI.
  • Etheremon — simulates a world of Ether monsters you can capture, transform.
  • SuperRare — a smart contract platform that allows artists to release limited-edition digital artwork tracked on the blockchain, making the art rare, verified and collectible.
  • Known Origin — brings together blockchain technology and digital artwork though the power of ERC721 backed digital arts assets.
  • Gizer — a real-time platform providing opportunities to gamers, hosts and services.
  • HiPrecious — high-end crypto-collectibles, luxuriously made in Paris.

Escrow-less auctions, a.k.a. “sell orders,” will be available for these items in the coming weeks. EDIT: Now they’re available!

Notes to developers:

If you’d like to make sure your tokens support buy orders and sell orders, you can follow our tutorial, or simply have your contract inherit from the OpenZeppelin ERC721 standard. Buy orders depend on the existence of the transferFrom method.

Placing buy orders and sell orders programmatically

Contact us if you’d like access — the OpenSea SDK is in private beta.

How we did it

We used the Wyvern protocol, a robust, security-audited protocol for the exchange of non-fungible assets on Ethereum. Huge thanks to the team at Wyvern for working closely. We’re super proud to be the first Wyvern relayer.

The future is exciting — come value it.


* Note: a free (plus gas) transaction is required to set up your account so that item owners can instantly accept your offers. See https://opensea.io/faq#bidding