In blockchain ecosystems, a claim contract functions as a secure, automated disbursement mechanism. It holds a reserve of tokens—often from a treasury or a minting event—and allows users who meet specific eligibility criteria to call a claim() function to receive their allotted amount. This design prevents the need for centralized batch transfers and puts the onus of initiating the transaction on the recipient, which can optimize gas efficiency and prevent tokens from being sent to inactive wallets. The contract's logic is immutable once deployed, ensuring a transparent and trustless distribution process.
LABS
Glossary
Claim Contract
A claim contract is a smart contract that holds tokens and allows users who meet predefined eligibility criteria to claim or withdraw their allocated tokens.
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definition
BLOCKCHAIN GLOSSARY
What is a Claim Contract?
A claim contract is a specialized smart contract that manages the distribution of tokens or assets to a predefined set of eligible addresses, typically based on a snapshot of a prior state, such as an airdrop, token migration, or protocol reward event.
The core mechanism relies on a Merkle proof or a similar cryptographic verification method. Instead of storing all eligible addresses on-chain (which is costly), the contract stores a single Merkle root hash. When a user attempts to claim, they submit a proof that cryptographically demonstrates their address and allocated amount are part of the original, verified dataset. The contract verifies this proof against the stored root. This architecture is a standard pattern for large-scale airdrops, as seen with protocols like Uniswap (UNI) and Arbitrum (ARB), where thousands of users claimed tokens from a single contract.
Beyond airdrops, claim contracts are pivotal for token migrations during network upgrades or tokenomic changes. For example, when a project launches a new token (V2) to replace an old one (V1), a claim contract allows V1 holders to seamlessly swap their tokens for the new version. They are also used for distributing protocol rewards, retroactive funding, and vesting schedules, where tokens become claimable over time or upon meeting certain conditions. The security of the claim process is paramount, as vulnerabilities in the contract logic or the initial data generation can lead to significant fund loss.
From a developer's perspective, interacting with a claim contract typically involves checking one's eligibility off-chain—often via a project's official interface—which generates the necessary Merkle proof. The user then signs a transaction calling the claim function with this proof as a parameter. Key considerations when auditing or using such contracts include ensuring the claim period has not expired, verifying the contract's address is official to avoid phishing, and understanding any locking or vesting clauses attached to the claimed tokens.
key-features
CLAIM CONTRACT
Key Features
A claim contract is a smart contract that manages the distribution of tokens or assets to a predefined set of eligible addresses. It is a core component of airdrops, token launches, and vesting schedules.
01
Merklized Distribution
Uses a Merkle tree to efficiently prove eligibility without storing all recipient data on-chain. The contract stores only the Merkle root, while users submit a Merkle proof to claim their allocated tokens. This minimizes gas costs and contract storage.
02
Permissionless Claiming
Allows any user to invoke the claim function if they possess a valid proof. The contract verifies the proof against the stored Merkle root and the caller's address, ensuring only eligible recipients can claim their specific allocation.
03
Vesting & Cliff Periods
Often incorporates time-locks to enforce vesting schedules. Features include:
- Cliff period: No tokens are claimable until a specific date.
- Linear vesting: Tokens become claimable gradually over time.
- Revocable allocations: Allows a deployer to claw back unclaimed tokens under certain conditions.
04
Gas Optimization
Designed to minimize transaction costs for users. Techniques include:
- Using Merkle proofs for O(1) verification.
- Batching multiple claims in a single transaction.
- Allowing the contract owner to fund gas reimbursements for claimants.
05
Common Implementations
Widely used in major ecosystems. Examples include:
- Uniswap's Merkle Distributor: A standard for ERC-20 airdrops.
- OpenZeppelin's
VestingWallet: A secure base contract for linear vesting. - Sablier & Superfluid: For real-time, streaming token distributions.
06
Security Considerations
Critical audit points for claim contracts:
- Proof verification: Must correctly validate the Merkle proof and prevent replay attacks.
- Access control: Admin functions (e.g., withdrawing unclaimed funds) should be properly restricted.
- Front-running: Designs should mitigate the risk of a malicious actor intercepting a claim transaction.
how-it-works
MECHANISM
How a Claim Contract Works
A technical breakdown of the automated smart contract logic that governs the distribution of tokens or assets to eligible recipients.
A claim contract is a specialized smart contract that automates the distribution of digital assets—such as tokens, NFTs, or airdropped rewards—to a predefined set of eligible addresses. It functions as a secure, trustless escrow and disbursement mechanism, replacing manual processes. The contract's core logic encodes the rules for eligibility, vesting schedules, and claim amounts, ensuring that only authorized users can withdraw their allocated assets after meeting specific conditions, like passing a snapshot check or completing a task.
The operational lifecycle of a claim contract typically involves three phases: initialization, claiming, and expiration. During initialization, the contract is deployed with locked funds and a merkle root or a permission list that cryptographically defines eligible claimants. In the claiming phase, users submit a transaction to the contract, often providing a merkle proof to verify their inclusion without revealing the entire list. Finally, after a set deadline or once all funds are distributed, the contract may expire, with any unclaimed assets often being retrievable by the deployer or burned.
Key technical components include access control mechanisms to prevent unauthorized claims, gas optimization for user-friendly interactions, and immutable vesting schedules that release tokens over time. For example, a project might deploy a claim contract for its community airdrop, where users can claim 25% of their tokens immediately, with the remainder vesting linearly over 12 months. This structure aligns incentives and prevents market dumping. Advanced implementations may integrate with oracles to trigger claims based on real-world events or incorporate multi-signature wallets for administrative control over the contract's parameters and emergency functions.
common-use-cases
CLAIM CONTRACT
Common Use Cases
A claim contract is a smart contract that manages the distribution of tokens or assets to a predefined set of eligible addresses. It is a core primitive for airdrops, vesting schedules, and reward distribution.
02
Vesting & Linear Unlocks
Claim contracts enforce time-based release schedules for team, investor, or advisor tokens. Instead of sending tokens directly, they are locked in the contract and become claimable according to a vesting curve (e.g., linear over 4 years).
- Mechanism: The contract calculates the vested amount based on block timestamp or cliff dates.
- Advantage: Provides transparency and security, preventing premature selling or mismanagement of treasury assets.
03
Liquidity Mining & Yield Distribution
Used in DeFi protocols to distribute governance tokens or protocol fees as rewards to liquidity providers (LPs) or stakers. Users stake LP tokens, accrue rewards, and then execute a claim transaction to receive them.
- Design Pattern: Often paired with a staking contract that tracks reward accrual.
- Benefit: Separates reward logic from core protocol contracts, enabling upgrades and flexible reward schemes.
04
Refunds & Dispute Resolution
In scenarios like a canceled token sale (ICO) or a hacked protocol reimbursement, a claim contract can manage the fair return of funds. It defines eligibility (e.g., contributors before a certain block) and allows users to withdraw their original contribution.
- Use Case: The Parity multisig wallet freeze incident led to claim contracts for affected users.
- Characteristic: Often includes a timelock or expiration to encourage timely action.
05
Cross-Chain Asset Bridging
In canonical token bridges, when assets are locked on Chain A and minted on Chain B, the claim contract on the destination chain holds the minting authority. A relayer submits a proof, and the contract verifies it (e.g., via light client or oracle) before allowing the user to claim the minted assets.
- Core Function: Acts as the verifiable minting endpoint on the destination chain.
- Security: The claim logic is the critical security layer preventing invalid mints.
06
Gas Optimization with Merkle Distributions
A specialized implementation for large-scale distributions. Instead of storing all eligible addresses (costly), the contract stores a single Merkle root. Users submit a Merkle proof (leaf, path, root) to prove inclusion in the set, making the claim transaction extremely gas-efficient for the contract.
- Technical Detail: The contract only needs to verify a cryptographic proof, not query storage.
- Result: Enables airdrops to hundreds of thousands of addresses with minimal deployment cost.
eligibility-mechanisms
ELIGIBILITY MECHANISMS
Claim Contract
A claim contract is a smart contract that programmatically verifies user eligibility and distributes tokens or NFTs as part of an airdrop, rewards program, or token generation event.
01
Core Function: Merkle Proof Verification
A common method for efficient, gas-less claiming. The contract stores a Merkle root representing all eligible addresses and their entitled amounts. Users submit a Merkle proof (a cryptographic path) to prove their inclusion in the list without the contract storing every address, significantly reducing on-chain gas costs.
02
Eligibility Criteria & Snapshot
Claim contracts enforce rules set by a prior snapshot. Common criteria include:
- Holding a minimum balance of a specific token at a past block height.
- Interacting with a protocol (e.g., providing liquidity, voting) within a defined period.
- Being on a pre-approved allowlist. The contract logic validates these conditions on-chain when a claim is attempted.
03
Vesting Schedules
To prevent immediate sell pressure, claim contracts often implement vesting. This locks a portion of the claimable tokens and releases them linearly over time (e.g., 25% unlocked at TGE, then 25% quarterly). The contract manages these time-locked balances for each user.
04
Security Considerations & Risks
As high-value targets, claim contracts require rigorous auditing. Key risks include:
- Reentrancy attacks on the withdrawal function.
- Signature replay attacks if using EIP-712 permits.
- Incorrect Merkle root or logic flaws allowing unauthorized claims.
- Front-running where bots intercept claim transactions.
05
Common Standards & Examples
While often custom-built, patterns emerge:
- ERC-20 claim contracts for standard token distributions.
- ERC-721/ERC-1155 claim contracts for NFT mints.
- EIP-712 signed messages for gas-less, meta-transaction claims.
- Real-world examples include the Uniswap UNI airdrop and Optimism OP distribution contracts.
06
The Claim Process Flow
- Off-chain: Project determines eligibility and generates claim list (often as a Merkle tree).
- Deployment: Claim contract is deployed with the root, token address, and vesting rules.
- User Action: User calls the
claim()function, providing proof (if required). - Validation: Contract verifies proof, checks if already claimed, and applies vesting logic.
- Transfer: If valid, tokens are transferred from the contract's treasury to the user.
security-considerations
CLAIM CONTRACT
Security Considerations
A claim contract is a smart contract that manages the distribution of tokens or assets to eligible recipients. Its security is paramount as it often holds significant value and must execute logic flawlessly to prevent loss or theft.
01
Access Control & Ownership
Proper access control is critical. The contract must have a secure, immutable owner or governance mechanism to manage privileged functions like:
- Updating the merkle root for eligibility proofs.
- Pausing/unpausing claims.
- Withdrawing unclaimed or excess funds. A common vulnerability is leaving these functions unprotected or using a single, potentially compromisable private key for ownership.
02
Merkle Proof Verification
The core security of a claim contract often relies on Merkle proof verification. Risks include:
- Front-running: Malicious actors can intercept and replay a user's valid proof transaction.
- Proof Replay: The contract must prevent double-spending by marking addresses as claimed.
- Root Manipulation: If the contract owner can update the Merkle root arbitrarily after deployment, they could create fraudulent claims. The root should be immutable or governed by a multi-sig/timelock.
03
Reentrancy & State Management
Like any contract handling funds, claim contracts are susceptible to reentrancy attacks if they use call to transfer assets before updating internal state (e.g., marking an address as claimed). The Checks-Effects-Interactions pattern is mandatory:
- Check eligibility and proof.
- Effect update the
claimed[address]state totrue. - Interact safely transfer tokens via
transferor a non-reentrant function.
04
Token Approval & Allowance Risks
If the claim contract requires users to grant a token allowance (e.g., for claiming vested tokens from a separate vault), it introduces risk:
- Users must approve the exact claim amount, not an infinite allowance, to limit exposure.
- The contract must not have arbitrary
transferFromcapabilities beyond the claim logic. - A flawed contract could be tricked into draining a user's entire token balance from another approved contract.
05
Front-End & Data Integrity
The security of the claim process depends on the integrity of off-chain components:
- The Merkle tree generation must be correct and verifiable. A single error invalidates proofs.
- The claim front-end or API serving proofs must be secure; a compromised server can provide malicious proofs.
- Users should be able to independently verify their inclusion in the Merkle root using public tools.
06
Gas Optimization & Denial-of-Service
Poorly optimized verification logic can lead to gas limit issues, causing transactions to fail and effectively creating a Denial-of-Service (DoS) for legitimate claimants. Considerations:
- Keep Merkle proof verification loops efficient.
- Avoid unbounded operations or complex storage writes during the claim.
- Ensure the contract has a fail-safe mechanism (e.g., an owner can rescue funds) if the logic becomes unusable.
TOKEN DISTRIBUTION MECHANISMS
Claim Contract vs. Custodial Distribution
A comparison of two primary methods for distributing tokens to a predefined list of recipients.
| Feature | Claim Contract | Custodial Distribution |
|---|---|---|
Smart Contract Role | Passive; holds tokens for user-initiated claims | Active; executes transfers to user wallets |
User Action Required | ||
Gas Fee Payer | User (claimant) | Project (distributor) |
On-Chain Merkle Proof | ||
Initial Token Lockup | In the claim contract | In the distributor's wallet |
Claim Expiry / Time Limit | ||
Typical Use Case | Airdrops, vesting schedules | Investor/team allocations, simple rewards |
Recipient Wallet Must Be EOA |
ecosystem-examples
CLAIM CONTRACT
Ecosystem Examples
Claim contracts are specialized smart contracts that manage the distribution of tokens or assets to eligible recipients. They are foundational to airdrops, vesting schedules, and reward distribution mechanisms across various blockchain ecosystems.
03
Team & Investor Token Vesting
Platforms like CoinList and Sablier use claim contracts to enforce vesting schedules. These contracts hold locked tokens and release them linearly over time (e.g., a 4-year vest with a 1-year cliff). Key features include:
- Cliff periods before any tokens are claimable.
- Linear vesting for steady releases.
- Revocable rights for the deploying entity in case of early departure.
05
Liquid Staking Derivative Claims
In protocols like Lido and Rocket Pool, claim contracts are used when withdrawing staked assets. For example, when unstaking stETH, users receive a withdrawal NFT that can later be redeemed via a claim contract for the underlying ETH once the withdrawal request is processed by the network. This separates the request from the fulfillment, managing asynchronous processes.
06
Cross-Chain Claim Bridges
Bridging protocols like Wormhole and LayerZero utilize claim contracts on the destination chain. When assets are locked on the source chain, a message is relayed, and a claim contract on the destination chain mints the wrapped assets. The user must invoke this contract to claim the bridged tokens, adding a pull-based security layer versus automatic minting.
CLAIM CONTRACT
Frequently Asked Questions
A claim contract is a specialized smart contract that manages the distribution of tokens or assets to eligible recipients. This section answers common questions about their purpose, mechanics, and security.
A claim contract is a smart contract that holds a reserve of tokens or other digital assets and facilitates their distribution to a predefined list of eligible addresses, often based on a merkle root or snapshot. Its primary function is to automate and secure the process of airdrops, token launches, or reward distributions by allowing users to submit a proof of eligibility to claim their allocated assets. This mechanism eliminates the need for manual, centralized distribution, reducing gas costs and the risk of errors. Notable examples include the Uniswap (UNI) airdrop contract and various DeFi protocol reward distributors.
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