Soulbound Token (SBT)
A non-transferable, publicly-verifiable digital token that represents an individual's credentials, affiliations, or achievements.
Soulbound Tokens (SBTs) are a proposed type of non-transferable Non-Fungible Token (NFT) designed to represent a person's or entity's identity, affiliations, or achievements within a decentralized ecosystem. Unlike standard NFTs which can be bought, sold, or traded, SBTs are permanently or semi-permanently bound to a specific [wallet address](/en/terms/wallet-address), akin to a digital identity credential. The concept, introduced by Vitalik Buterin and others, aims to address issues of Sybil attacks and [decentralized identity management](/en/terms/decentralized-identity-management). SBTs could be issued by various entities (e.g., universities for degrees, DAOs for membership) and aggregated to form a comprehensive digital reputation. The technical implementation typically involves standard ERC-721 or ERC-1155 token contracts, with the key difference being the enforced non-transferability, often managed through smart contract logic or off-chain attestations. Challenges include privacy concerns, the potential for social stigma associated with certain SBTs, and the development of robust standards for their issuance and verification.
graph LR
Center["Soulbound Token (SBT)"]:::main
Rel_non_fungible_token_nft["non-fungible-token-nft"]:::related -.-> Center
click Rel_non_fungible_token_nft "/terms/non-fungible-token-nft"
Rel_nft["nft"]:::related -.-> Center
click Rel_nft "/terms/nft"
Rel_blockchain["blockchain"]:::related -.-> Center
click Rel_blockchain "/terms/blockchain"
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🧠 Knowledge Check
🧒 Explain Like I'm 5
🌍 Imagine a digital trophy or a school diploma that you can't sell or give to anyone else. It's 'stuck' to your digital profile forever to prove that YOU were the one who earned it. That's a Soulbound [Token](/en/terms/token).
🤓 Expert Deep Dive
SBTs represent a paradigm shift from fungible and transferable NFTs towards verifiable credentials. Their non-transferability is a core design choice, differentiating them from existing NFT standards. While ERC-721 can be adapted, dedicated standards (like ERC-5114, though still evolving) might emerge to better handle SBT semantics, such as revocation and attestation management. The 'soul' aspect implies a direct link to a wallet, raising questions about wallet ownership vs. individual identity and the potential for wallet fragmentation to dilute reputation. Privacy is a significant concern; selective disclosure mechanisms or zero-knowledge proofs may be necessary to allow users to control which SBTs are revealed in different contexts. The economic implications are also profound, potentially creating new markets for reputation and identity services.