How is NFT Metadata Decentralization Implemented on OpenSea?

NFTs are unique tokens with decentralized ownership. The question of "who owns this token" is stored and tracked simultaneously by multiple computers, preventing anyone from tampering with ownership without authorization. However, NFT-related media attachments and content (collectively called "NFT metadata") have never achieved decentralization, because storing and modifying data directly within smart contracts incurs high gas costs. Without decentralization, collectors cannot trust that a token's metadata is complete and immutable.