The Promise vs. Reality of NFT Decentralization: An Empirical Study of Storage Strategies and Defects

The value of NFTs (Non-Fungible Tokens) is built on the promise of decentralization, permanence, and immutability. However, a significant gap exists between this perception and reality. In this paper, we collect over 16 million real-world NFTs and systematically analyze their storage locations. Our results reveal a widespread reliance on fragile off-chain storage and uncover a ''Blue-chip Trap'' where high-value assets depend heavily on centralized infrastructure, rendering the promise of decentralization largely misleading. Consequently, we propose the first taxonomy of NFT storage defects, classifying eight distinct vulnerabilities into access failure, tamperability, and forgeability. Through a large-scale empirical analysis, we map real-world assets to this taxonomy, confirming the widespread prevalence of these defects across the ecosystem. Finally, we analyze the impact of these defects on assets, users, and the ecosystem, and systematically quantify their severity using the Common Vulnerability Scoring System (CVSS). Our assessment reveals that all identified defects pose substantial risks, providing a reference for developers to design more secure storage strategies.