Crypto Split

The Problem Splitting bills with friends has always been a source of friction in social and professional settings. Traditional methods involve manual calculations, IOUs, and the awkward task of chasing people for money. The rise of payment apps like Venmo and Splitwise improved this experience in Web2, but they still rely on centralized platforms, require trust in intermediaries, and charge fees. In the Web3 ecosystem, the problem becomes even more complex as people use different wallets, prefer different tokens, and operate across multiple chains. There's no unified, trustless way to split expenses that leverages the transparency and automation that blockchain technology provides.

The Solution CryptoSplit brings the simplicity of traditional bill-splitting apps to Web3 while removing the need for intermediaries. The platform allows anyone to create a bill by specifying a description, total amount, and list of participant wallet addresses. The smart contract automatically calculates each person's share and tracks payments on-chain. Participants can pay their portion directly to the bill creator with a single transaction, and the blockchain serves as an immutable record of who has paid and who hasn't. There's no need to trust a central platform or worry about disputed payments, everything is transparent and verifiable.

CryptoSplit is a full-stack decentralized application built with three core components working together to create a seamless bill-splitting experience.

Smart Contract Foundation The heart of the system is a Solidity smart contract that handles all payment logic. Written in Solidity 0.8.20, the contract uses a struct-based architecture where each bill contains a description, total amount, creator address, participant list, and payment tracking. The contract automatically calculates equal splits among participants and maintains an immutable record of who has paid.

Security was paramount throughout development. The contract implements reentrancy guards to prevent fund drainage attacks, uses custom errors for gas optimization, and validates all inputs to ensure only authorized participants can make payments. The payment tracking system uses efficient mappings for constant-time lookups regardless of participant count. Once all participants pay, the bill creator can withdraw the collected funds with a single transaction.

Development and Testing Foundry serves as the development framework, chosen for its speed and Solidity-native testing capabilities. The built-in Anvil blockchain enables instant local testing without external dependencies. A comprehensive test suite written entirely in Solidity covers all core functionality including bill creation, payments, withdrawals, and edge cases. All tests pass successfully, validating the contract's behavior under various conditions. Deployment is automated through Forge scripts that work identically across local, testnet, and mainnet environments. Frontend Experience The interface is built with vanilla JavaScript and Ethers.js, deliberately avoiding frameworks to maintain simplicity and reduce dependencies. MetaMask integration handles wallet connections and transaction signing, with careful error handling for edge cases like rejected connections or network changes. The design uses modern UI patterns with gradients and card layouts that work across devices.

The user flow is streamlined: connect wallet, create a bill with participant addresses, and the system displays payment information instantly. Participants pay their share with one click, and the interface updates in real-time as payments arrive. LocalStorage caches bill data for performance while the blockchain remains the authoritative source.

Gas Optimization Every aspect was optimized for gas efficiency. Custom errors reduce costs by fifty percent compared to traditional require statements. Storage variables are packed efficiently, and the contract minimizes expensive storage writes. Payment operations follow the checks-effects-interactions pattern for both security and efficiency. Typical transactions cost around 50,000 to 150,000 gas, making the platform practical for everyday use.

Production Architecture CryptoSplit requires no backend servers or databases. The smart contract runs on any EVM blockchain, and the frontend can be hosted anywhere including IPFS for complete decentralization. Setup scripts automate the entire deployment process, allowing anyone to launch a working instance in minutes. The codebase follows best practices with clear documentation, making it maintainable and forkable.

The project demonstrates that Web3 applications can be both powerful and simple. By hiding blockchain complexity behind familiar interfaces, it makes cryptocurrency payments accessible while maintaining the transparency and trustlessness that makes decentralization valuable.