Home/Blockchain/Marketplace Game/How Listings Work

🏷️ Listings: Fixed Price vs Auctions

Understand listing types and how orders are matched on-chain

Buy, sell, and bid on NFTs in a simulated marketplace

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📝 How NFT Listings Work

When you "list" an NFT, you're not actually sending it anywhere—it stays in your wallet. Instead, you're creating a cryptographically signed order that gives a smart contract permission to transfer your NFT if someone pays your price. This off-chain signature model is what makes "gas-free" listings possible.

🎛️ Interactive: Listing Type Simulator

Adjust price and compare different listing strategies. Each type has trade-offs in speed, gas costs, and price discovery.

10 ETH
1 ETH12.5 ETH25 ETH37.5 ETH50 ETH
💰

Fixed Price

Set a price, buyer pays immediately

Gas Cost
Low (off-chain signature)
Best For
Quick sales at known prices
Start Price
10 ETH
Example Scenario:

List CryptoPunk #1234 for 10 ETH. Buyer clicks "Buy Now", pays 10 ETH + gas, gets NFT instantly.

Pros:
  • •Instant sale
  • •No gas to list
  • •Simple UX
Cons:
  • •Miss price discovery
  • •Can't capture upside in hot market

🔄 The Listing Process (Step-by-Step)

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1. Approve NFT Contract
Grant marketplace permission to transfer your NFT
nftContract.approve(marketplaceAddress, tokenId)
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2. Sign Listing Order
Create off-chain signature with price and expiry
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📤
3. Upload to Marketplace
Marketplace indexes your signed order
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4. Buyer Purchases
Buyer calls smart contract with your signature
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🔐 Off-Chain vs On-Chain

Off-Chain Order (Free):

Sign a message with your wallet. No gas. Order lives in marketplace database. Most platforms use this for fixed-price listings (OpenSea Seaport, Blur).

On-Chain Listing (Costs Gas):

Transaction creates contract state. Costs $5-50 in gas. Required for auctions and Dutch auctions. Order is immutable once confirmed.

💡 Why Gas-Free Listings Work

Instead of writing to the blockchain, you sign a message saying "I authorize this marketplace contract to transfer my NFT for X ETH until timestamp Y." The signature is stored off-chain. When someone buys, they pay gas to execute the trade using your signature as proof of authorization.

Security: Marketplace can't execute without a buyer paying your price. You can cancel anytime by revoking approval.

💡 Key Insight

The genius of modern NFT marketplaces is off-chain order matching with on-chain settlement. You sign orders for free, the marketplace aggregates them into a searchable database, and buyers pay gas to execute trades. This model keeps listing costs at zero while maintaining the trustless, non-custodial properties of blockchain. Your NFT never leaves your wallet until the exact moment someone pays your price and the smart contract atomically swaps ownership.

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