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Project · Intermediate · about 16 hours

An NFT collection with an allowlist mint

Build an ERC-721 collection with a Merkle-proof allowlist, a public mint phase, royalties metadata and withdrawals, fully tested in Foundry.

Skills:Blockchain fundamentals, Smart contracts and Solidity, Automated testing

Part of: Blockchain Developer

Data and licences

Brief

NFT drops combine several patterns every contract developer should know: Merkle proofs, phased sales, supply limits and safe withdrawals. Use a local Anvil chain and, when you deploy publicly, a testnet such as Sepolia with free test ether from a faucet. Never use real funds or a wallet that holds any, and never paste a private key into code or a website.

What to build

  1. Write an ERC-721 contract with a maximum supply, an owner-controlled phase switch and a per-wallet mint limit

  2. Implement the allowlist phase with a Merkle root stored on chain and proofs supplied by minters

  3. Write a TypeScript or Python script that builds the tree from a CSV of addresses and outputs proofs

  4. Add ERC-2981 royalty information and token metadata on IPFS or another content-addressed store

  5. Test each phase, the limits, wrong proofs and the owner withdrawal, and deploy to Anvil with a script

Deliverables

  • Repository with src/, test/, scripts/merkle/, metadata and README.md

How it is graded

Reviewers mint with a wrong proof, exceed the wallet limit and mint past the cap, and check each fails with a clear error.

Stretch

Add a reveal step where metadata is hidden until a set time, and explain the trust assumptions.

Deliverables

  • An ERC-721 contract on OpenZeppelin with allowlist and public mint phases, a supply cap and per-wallet limits
  • A script that builds the Merkle tree of allowlisted addresses and produces proofs
  • Metadata served from content-addressed storage, with ERC-2981 royalty information
  • Tests for every phase, limit and revert, plus a fuzz test on the per-wallet limit

How a reviewer grades it

CriterionWeightWhat good looks like
Mint phases, caps and limits are enforced correctly30%
Merkle allowlist is correct and cheap to verify25%
Tests cover every phase and revert30%
Metadata, royalties and documentation15%