NFT compatibility is guaranteed through standardization and adherence to the ERC-721 or ERC-1155 token standards on the Ethereum blockchain. These standards define the basic rules and functions for creating, transferring, and storing NFTs, ensuring that NFTs are interoperable across different platforms and marketplaces. Additionally, smart contracts are used to ensure that transactions involving NFTs are secure and immutable, preventing any unauthorized modifications or duplication. As long as NFT creators and platforms follow these standards and best practices, NFT compatibility can be guaranteed.