A soulbound token (SBT) is a non-transferable NFT permanently bound to a specific wallet address. Once received, it cannot be sold, traded, or moved to another wallet. SBTs represent credentials, achievements, or affiliations that should not be tradeable: university degrees, employment history, community membership, proof of attendance, or reputation scores.
What Is a Soulbound Token?
3 min read
The short version
A soulbound token is like a badge sewn onto your jacket that cannot be removed or given away. It proves something about YOU specifically: that you attended an event, completed a course, or belong to a community. Because it cannot be transferred, it cannot be faked by buying someone else's credential. Your wallet becomes your verifiable resume.
How It Works
Implementation: the smart contract overrides or omits the transfer function, making tokens non-transferable after minting. The token can be minted to an address (by an authorized issuer) and optionally revoked (burned by the issuer if a credential expires). ERC-5192 proposes a standard interface for soulbound tokens. Use cases: proof of attendance (POAPs are optionally soulbound), DAO membership (non-transferable voting rights based on contribution, not purchase), identity verification (KYC attestation without revealing personal data), skill credentials (completing an audit course, contributing to a protocol), and credit scoring (on-chain reputation based on lending/repayment history).
Using SBTs for DAO contribution-based voting
A DAO wants to give voting power based on actual contribution, not just token wealth. They issue SBTs: "Core Contributor" (4 votes per proposal), "Active Participant" (2 votes), "Community Member" (1 vote). SBTs are minted by a reputation committee based on measurable on-chain and off-chain contributions. Because they are non-transferable, you cannot buy your way to "Core Contributor" status. If someone leaves the community, their SBT can be revoked. Voting power reflects actual engagement rather than wealth. This creates a more meritocratic governance system than pure token-weighted voting.
What People Get Wrong
Soulbound tokens are a new invention
The concept was popularized by Vitalik Buterin in a 2022 paper, but non-transferable tokens existed before (POAPs, some access tokens). SBT formalized the concept and proposed it as a foundational building block for decentralized identity and reputation.
If you lose your wallet, you lose all your credentials
This is a genuine concern and the primary UX challenge. Solutions being explored: social recovery wallets (where SBTs can be recovered to a new address via guardians), issuer re-issuance (the credential issuer mints a new SBT to your new address), and community-recovery mechanisms.
SBTs solve the identity problem completely
They are one building block, not a complete solution. SBTs do not prevent a person from creating multiple wallets to accumulate multiple sets of credentials (Sybil attacks). Combining SBTs with proof-of-personhood protocols is needed for robust identity systems.
Keep Reading
Sources & Further Reading
- Decentralized Society Paper (Vitalik et al.)
The original academic paper proposing soulbound tokens for decentralized identity
Questions People Also Ask
- Can I refuse a soulbound token?
- This depends on the implementation. Some designs require the recipient to claim/accept the SBT. Others allow issuers to mint directly to any address. Unwanted SBTs that cannot be burned by the recipient raise privacy and consent concerns still being debated in the ecosystem.
- Are POAPs soulbound?
- Standard POAPs (Proof of Attendance Protocol) are transferable ERC-721 tokens. Some issuers mark them as "non-transferable" through social norms or marketplace delisting, but this is not technically enforced on-chain in the default POAP implementation. True SBTs would be non-transferable at the contract level.
- What chains support soulbound tokens?
- Any EVM chain can deploy SBT contracts (Ethereum, Polygon, Arbitrum, etc.). Binance launched BAB (Binance Account Bound) tokens. Polygon has a soulbound NFT framework. The concept is chain-agnostic since it is just a smart contract pattern that disables transfers.