Sending money on crypto rails shouldn’t require technical knowledge. No seed phrases. No gas prep. No platform fragmentation. No waiting for confirmations.

Send removes all of that friction.

Our implementation of ERC-4337 account abstraction is one piece of the puzzle, it lets you sign with Face ID and Send USDC without owning ETH -  but it’s only the beginning.

Under the hood, Send is a three-layer architecture:

• a unified frontend that ships everywhere at once,
• a real-time backend designed for reliability,
• and a smart-contract wallet system that eliminates gas management entirely.

The result is simple: payments that feel instant, familiar, and self-custodial -  powered by sophisticated engineering you never have to think about.

First, a quick summary

What you experience:

• No ETH, no problem — Our paymasters let users pay gas fees with any erc 20 token like USDC and in some cases, sponsor the transaction completely.
• Sign with Face ID — No seed phrases to memorize or lose. Fast confirmations — Payments show up in seconds. Base L2 and real-time indexing eliminate the wait.
• Works everywhere — Same experience on web, iOS, and Android. Unified codebase means no platform fragmentation.
• Open and auditable — Every line of code public on GitHub. Security through transparency.

The Challenge: Crypto Wallets Are Still Too Hard

Traditional crypto wallets require you to:

1. Write down 12 random words and never lose them
2. Buy ETH just to pay for gas
3. Learn what "gas" even means
4. Copy 42-character addresses and pray you didn't typo

After 10 years of crypto innovation, this remains the standard. We asked ourselves: what if none of this was necessary?

Our Architecture: Three Layers

Send's architecture eliminates friction at three levels: frontend, backend, and blockchain.

Frontend: Same Experience, Every Platform

Open Send on your iPhone. Switch to your laptop. Everything works identically. Your payment history, contacts, and settings sync instantly.

We use a unified codebase that deploys to web, iOS, and Android simultaneously. Shared business logic handles payments, user management, and blockchain interactions. Platform-specific interfaces use Tamagui to feel native while sharing approximately 80% of component code.

When we ship a feature, it goes live everywhere at once.

Backend: Infrastructure Built for Reliability

You Send 100 USDC to /alice. Within seconds, both of you see the payment confirmed with push notifications. The infrastructure is designed to minimize failed transfers and stuck payments.

Your tap queries our Supabase database to resolve /alice's Sendtag to her blockchain address. Row-level security policies verify your permissions. Your signed transaction hits Base L2 and confirms in 2 seconds.

Our Shovel indexer monitors Base continuously. When your transaction confirms, it writes the data to PostgreSQL and triggers WebSocket subscriptions for instant updates.

Our Temporal workflow engine ensures reliable completion even if a server crashes mid-process

Blockchain: The Architecture That Covers Gas Fees

You've never bought ETH. You don't know what "gas" means. You just Send money to /alice with Face ID.

Base L2: Speed and affordability

We build on Base, Coinbase's Layer 2 network. Transactions confirm in 2 seconds with sub-cent fees. Full Ethereum compatibility means all standard tools and contracts work seamlessly.

ERC-4337 Account Abstraction: The breakthrough

Traditional wallets require you to own ETH before Sending any token. We flip this model.

Each Send user gets a smart contract wallet with capabilities normal wallets can't match:

• Passkeys: Sign transactions with Face ID or Touch ID. No seed phrases to manage.
• Batch operations: Multiple actions in a single transaction.
• Flexible recovery: Multi-signature recovery that protects your funds without exposing private keys.
• Send Account Contracts: Your programmable wallet

Every Send user gets their own SendAccount smart contract deployed to Base. These verify WebAuthn signatures onchain, execute multi-step operations atomically, and integrate with our paymaster for sponsored transactions.

Open Source: Building in Public

Send is fully open source. Every line of code is publicly auditable on GitHub.

Transparency builds trust. Users can verify exactly how their money is being managed. Security researchers and contributors make our codebase more robust. Anyone can fork, modify, or self-host Send for their own use cases.

What's Next

• This architecture enables features that traditional fintech can't match:
• Programmable payments: Recurring subscriptions, conditional transfers, payment streaming
• Cross-chain support: We're exploring expansion beyond Base to other blockchains like Canton Network.
• DeFi integrations: Swaps, lending, and yield with the same simple UX
• Decentralized identity: Your Sendtag as portable identity across the crypto ecosystem

The Bottom Line

Great technology should be invisible.

You shouldn't need to understand chain IDs, account abstraction, Layer 2 scaling, or ERC-4337 bundlers to Send money to your friends.

Under the hood, Send combines sophisticated blockchain engineering with an obsessive focus on user experience. All in service of one goal: making crypto payments actually work for everyone.

Try Send at Send.app

Want to dig deeper? Our entire codebase is open source at github.com/0xSend/Sendapp

‍