On opensea, if you sell on Ethereum blockchain with a fixed price and say a month time, and during that month someone want/try to buy it in that price, do you (the seller) have to pay any gas fee?

Do you even need to know anything after the listing in that fixed price?

To give some context: I was surprised opensea didn't ask for any gas fee when listing the sell on Ethereum, but was wondering if I need to check in from time to time (and pay gas), in case someone try to buy it in the exact price it was listed

1 Answer 1


No, this is because what OpenSea does is collect a signature from your wallet and hosts it on the site.

When a user goes to look at your asset, OpenSea shows them that signature and if they so wish, they can bundle that signature, along with a transaction that they broadcast and pay the gas fees for. The OpenSea marketplace contract will then execute the trade, using your signature as proof that you did wish to sell the asset for the given price within the given timeframe.

This is also true for things such as bid offers, OpenSea hosts them and the owner of the asset can use that signature to execute a transaction in which they sell the asset to the bidder.

This is also why when you are cancelling bids / listings on OpenSea, a gas fee (sending a transaction) is required. A malicious actor could save the signature for later use (OpenSea freely gives the signatures out), and then use it in a transaction to purchase your asset (vice-versa for bids). Cancelling a bid / listing will send a transaction containing the signature you previously generated, with instructions to disallow that signature for further use. This of course incurs a gas fee.

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