Chill'Split 🧾💸

A Web3-powered group expense tracker – built to feel Web2.

Chill'Split lets friends and groups split expenses in a transparent, trustless, and automated way — powered by smart contracts, but designed for everyday users. It abstracts away blockchain complexity using modern wallet tech, gas sponsorship, and automatic reimbursements.

• Live on Base Sepolia: Try it
• Or watch the video demo : Watch the video

🧭 Overview

❓ What Is Chill'Split?

Chill'Split is the next evolution of group expense apps (like Tricount or Splitwise), fully decentralized. Users can:

• Create or join a group via code
• Add expenses
• Validate or reject expenses on-chain
• Settle balances automatically, using USDC (only USDC for now)
• Reimburse transparently — without needing to "trust" anyone

Despite being on-chain, Chill'Split is designed to feel like a regular web app — no confusing wallet popups or crypto jargon (except for the on-ramp process unfortunately).

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🧪 Key Features

• 🏗 Group-specific smart contracts: Each group gets its own deployed contract to track members, expenses, validations, and balances.
• 🔐 Fully on-chain logic: Every validation, approval, and settlement happens on the blockchain.
• 🚫 No manual signatures: Using Dynamic.xyz, all wallet interactions are abstracted (Gasless txs, EIP-7702, EIP-2612).
• 🔄 Gas sponsored: No user has to pay transaction fees — even for on-chain calls ( txs are sponsored in server actions).
• 💸 On-ramping support: Wallets can be funded with fiat using Transak, built into the UI (on top of the current dynamic on-ramp providers)*
• 📱 Mobile-first experience: Tailored UI and authentication for users unfamiliar with Web3.

*Transak was added on top of dynamic embedded on-ramp service, because I wanted to have the quickest on-ramp workflow possible for the end user

⚙️ Tech Stack

🧱 Frameworks & Libraries

• Next.js 15 App Router – React framework with SSR & API routes
• TypeScript – End-to-end type safety
• Tailwind CSS – Utility-first styling
• Radix UI – Accessible primitives for components
• Lucide-react – Styled icons and symbols
• viem – Modern Ethereum-compatible client for smart contract interaction

🔐 Wallet & Auth

• Dynamic.xyz – Wallet abstraction and authentication (supports social login, signature hiding)
• EIP-7702 - Enable gasless transactions sponsored in server actions
• EIP-2612 & Permit – For signature-free USDC approvals

🧾 Payments & Onramping

• Transak – Fiat-to-crypto on-ramp integrated into the onboarding flow
• For the off-ramp process, users can always use the embedded Dynamic workflow (a nice future update would be to add a simpler workflow here)

🔗 Smart Contract Architecture

• Factory Contract – Deploys and tracks individual group contracts.
• Group Contract – Manages:
  • Participants & pseudonyms
  • Expenses and validator logic
  • Settlement and balance updates
  • Reimbursements and payout flow

Every group action (add expense, validate, close, reimburse) is executed on-chain. Users can verify everything on block explorers — no hidden balances or calculations.

🚀 Getting Started

# 1. Clone the repo
git clone https://github.com/your-username/chillsplit.git

# 2. Install dependencies
npm install

# 3. Set up environment variables (.env.local)
# Include Dynamic.xyz keys, Transak API, RPCs, etc.

# 4. Run the dev server
npm run dev

📦 Build & Deploy

For production:

npm run build
npm run start

💬 Contact

Built with ❤️ by Thomas FEVRE
Feel free to open issues or suggestions!

TODO

• Show user USDC balance (even if embedded wallet has it)
• Simulate contract before actually write in server actions to avoid gas waste
• handle the off-ramp with transak if simpler & quicker than embedded wallet options