Every dollar accounted for

An API for moving money between accounts, with atomic transfers, streaming balances, and a built-in audit trail.

User$0Exchange$0BTC 10x

What you get

Financial primitives that handle the hard parts so you don't have to.

Source
-$1,000
Destination
+$1,000

Atomic Transfers

Source and destination balances update in the same operation.

credit+$1,000
balance$1,000 USD
completed47ms

Real-Time Streaming

Balance changes and operation events stream to your code over WebSocket.

transfer created
debit: -$1,000
credit: +$1,000
completed (47ms)

Complete Audit Trail

Every transfer links to the operation that created it and the full event chain.

From components to product

Pick the pieces you need — balances, trading, payments — and ship a working product in days.

yourapp.com
Balance
$1,250.00
↑ 12.5%today
Recent
Payment received+$500
Fee collected+$0.05
Withdrawal-$200
BTC-USD$67,842
Buy
Sell
Payment Link
Pay $25.00

Six building blocks, roughly fifty lines of code, and a product your users can pay with

Who builds with Arca

For Builders
sdk.ts
await arca.transfer({ ... })
✓ completed — 47ms
Explorer
/wallets/user-42
$1,250.00

The SDK and the Explorer show the same balances because they read from the same source of truth.

Start building
For Crypto Projects
BTC-USDHL
$67,842
10x Long
entry $67,200
Unrealized P&L+$642.00
Arca margin held$6,784.20

Your dev says 'ship in a week.' They mean it.

See why Arca
For Creators
“Make a payment app”
await arca.transfer({ ... })
$10.00
received

The SDK is named and typed so AI-generated code runs correctly without hand-editing.

Build with AI

The Explorer

Watch balances, events, and operations update in real time.

portal.arcaos.io/explorer
Objects
▼ /wallets
/treasury
/user-42
/user-107
▶ /exchange
▶ /fees
/wallets/treasury
$48,750.00
USD · Updated 2s ago
Settled
$48,750
Departing
$0.00
Arriving
$2,100

Engineering principles

Financial infrastructure requires guarantees, not best-effort. These aren't aspirations — they're enforced by the platform.

Conservation of value
Balances always sum correctly — every transfer is double-entry, and invariants are verified continuously
Immutable history
Operations, events, and deltas are append-only. Nothing is silently edited or deleted
Custody separation
Signing keys never leave your infrastructure. Arca holds the ledger; you hold the keys
Sub-500ms streaming
Balance changes, fills, and valuations stream to your app within 500ms of the underlying event
Built-in audit trail
Every state change traces back to its originating operation — no gaps, no orphaned mutations
Managed infrastructure
Arca runs the platform — monitoring, incident response, and financial integrity checks. You build; we operate

Get early access

Join the waitlist to be first in line.