SwapJar

Receive payments across multiple chains, automatically swapped to your favorite stablecoin via 1inch Fusion+.

SwapJar is a crypto-native payment collection platform for creators, fundraisers, and freelancers. With one simple IPFS-backed link, anyone can send payments in any token — including low fee chains like Stellar — and the receiver will automatically get their chosen stablecoin (USDC, DAI, etc.) using 1inch Fusion+ cross-chain swaps.

Example page: https://swapjar.vercel.app/tip/bafkreibjvuqemz7ajpwabr62kmpgglx636knrn4ybbffwtcwfsi3i5ypam

Demo url: https://swapjar.vercel.app

Demo video: https://youtu.be/RNcDxn0VMPw

Example transaction through SwapJar from ETH sender to USDC recipient mainnet: https://etherscan.io/tx/0x1593bcff0fe781705a5274e875433d784675aaa7b86c83b27dbe9bec8d64b9f4

Example swap + bridge payment through mainnet to stellar (mainnet): https://steexp.com/account/GAIFMUVXX73LCIC7RWEQJKNZF6DBI7VBOVMZUACHPZ3ZFBEYWL75IMIF/payments

Built for the <a href="https://ethglobal.com/events/unite/home">EthGlobal Unite Defi Hackathon 2025</a>.

Going after the below categories

• 1inch – Fullstack dApp using APIs and Fusion+
• 1inch – Fusion+ Extension (non-EVM chain: Stellar)
• Stellar – Best use of Stellar x 1inch

Current payment collection solutions in crypto face several critical limitations:

• Single-chain constraint: Most payment jars only accept tokens from one blockchain, forcing users to hold specific assets or pay bridge fees manually
• Token volatility risk: Recipients often receive volatile tokens (ETH, random memecoins) instead of stable value, creating unwanted exposure
• High gas costs: Traditional swaps require recipients to pay gas fees to convert payments to stablecoins, eating into small payment amounts
• Poor UX for non-crypto users: Supporters need to understand specific tokens, networks, and wallet management
• Limited cross-chain support: No seamless way for users on non-EVM chains (like Stellar) to send payments to EVM users
• Manual conversion overhead: Recipients must manually swap each payment, creating friction and ongoing maintenance

Solution

SwapJar solves these problems by creating a universal, gasless payment collection experience powered by 1inch Fusion+ and IPFS:

🎯 One Link, Any Token: Recipients create a single IPFS-backed shareable link that accepts payments in ANY token from multiple chains (Ethereum, Base, Optimism, Stellar), removing blockchain complexity for supporters.

🎨 Perfect for Creators & Events: Whether you're a content creator collecting fan support, a couple setting up a wedding fund, or a freelancer receiving project payments, SwapJar handles multi-chain payments seamlessly.

⚡ Gasless Auto-Swaps: Using 1inch Fusion+, all incoming payments are automatically swapped to the recipient's preferred stablecoin without them paying any gas fees, ensuring they keep 100% of the payment value.

🌉 Cross-Chain Bridge Integration: We extended Fusion+ capabilities to support Stellar through our custom bridge integration with Circle CCTP and real-time price feeds, allowing XLM and Stellar USDC holders to seamlessly send payments to EVM users with automatic conversion rates.

💰 Stable Value Guarantee: Recipients always receive stablecoins (USDC, DAI, USDT), eliminating volatility risk and providing predictable value regardless of what token was sent.

🔄 Intent-Based Architecture: Leveraging Fusion+ intent-based swaps means better prices, MEV protection, and no failed transactions due to slippage, ensuring optimal execution for all payments.

Challenges we ran into

Cross-Chain Complexity: Integrating Stellar with EVM chains required building custom bridge monitoring and real-time price feed integration. We had to handle different transaction finality models and ensure atomic cross-chain operations.

Fusion+ Integration: Working with intent-based swaps required understanding the order flow and properly handling order settlement timing. We needed to build robust monitoring to track order status and handle edge cases, plus implement fallback mechanisms when API quotas are exceeded.

Gas Optimization: Even though Fusion+ is gasless for users, our backend relay service needed to optimize gas costs for posting intents and bridging operations while maintaining profitability and handling token address validation across multiple chains.

Wallet UX: Supporting both EVM (WalletConnect) and Stellar (Freighter) wallets in a single interface required careful state management and error handling for different wallet connection patterns, plus cross-chain quote calculations.

Real-time Price Feeds: Building accurate cross-chain quotes required integrating multiple price sources (1inch, Stellar orderbook, CoinGecko fallback) and handling rate limiting, API failures, and ensuring quotes remain accurate across different market conditions.

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🎯 Project Goals

• Create a production-ready payment collection app powered by 1inch
• Use as many 1inch APIs as possible: Fusion+ Swap, Price Feeds, Token Metadata, Wallet Balances, Web3
• Extend Fusion+ cross-chain swap support to Stellar via custom bridge integration
• Offer a simple and gas-efficient payment experience for both EVM and non-EVM users with IPFS-backed payment links

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🔄 How It Works

✨ 1. User Creates a Payment Collection Link

• Sets wallet address, preferred stablecoin
• Generates IPFS-backed shareable link (e.g., https://swapjar.vercel.app/tip/bafkrei...)
• Perfect for creator donation pages, wedding registries, freelance invoices

💸 2. Supporter Sends Payment

• Supports any ERC-20 token from Ethereum, Optimism, Base, Polygon, Arbitrum
• Supports USDC or XLM from Stellar via custom bridge integration
• Real-time cross-chain quote calculation with multiple fallback price feeds

🔁 3. Tokens Swapped Automatically via Fusion+

• EVM tokens are swapped via 1inch Fusion+ into stablecoin with optimal execution
• Stellar payments are bridged to EVM (via Circle CCTP for USDC, custom bridge for XLM), then swapped via Fusion+
• Automatic fallback to regular 1inch swaps if Fusion+ is unavailable

✅ 4. Receiver Gets Stablecoin

• Recipient receives stablecoin (e.g., USDC) in their wallet

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🔌 1inch APIs Used

1. Fusion+ Swap API: Used to create gasless, intent-based swaps with optimal execution
2. `Token Metadata API: Shows logos, symbols, decimals for all supported tokens
3. `Price Quotes API: Used to calculate payment equivalent and cross-chain rates
4. `Wallet Balances API: Display real-time wallet status across multiple chains
5. `Web3 API: Submit Fusion+ swap transactions from backend relay service

Potential future work

• Advanced Stellar Integration: Implement bidirectional swaps allowing EVM users to send payments that automatically convert to XLM on Stellar, plus support for additional Stellar assets and integration with Stellar's native DEX for better exchange rates.

• Enhanced Cross-Chain Support: Expand beyond Stellar to support additional non-EVM chains like Solana, Cosmos, and Bitcoin Lightning Network, creating a truly universal payment collection platform that works across all major blockchain ecosystems.

• Smart Payment Routing: Develop intelligent routing algorithms that automatically select the optimal path (direct swap vs. cross-chain bridge) based on real-time fees, liquidity, and execution speed to minimize costs and maximize value for recipients.

See full information and more screenshots on the github here: https://github.com/cbonoz/unite25