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The Nxos API lets you move money between fiat and crypto programmatically. You can hold balances in multiple currencies, convert between assets, and pay out to bank accounts or blockchain wallets. All interaction happens through a single REST API authenticated with API keys.

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Where to start

Authentication

Create and manage API keys.

Conventions

Pagination, amounts, timestamps, and error handling.

Onramp guide

Accept fiat, convert to crypto, send on-chain.

Offramp guide

Receive crypto, convert to fiat, pay out to a bank.

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Resource hierarchy

Every API key belongs to an organization. An organization contains one or more accounts, and accounts are the central container for all monetary activity on the platform. 
Organization
├── API Keys
└── Accounts
    ├── Balances          USD, USDC, EUR, USDT
    ├── Funding Methods   bank accounts, crypto wallets
    └── Beneficiaries     payout recipients
ResourceDescription
OrganizationYour company. Owns accounts and API keys.
AccountHolds multi-currency balances. Source for all transactions.
BeneficiaryA registered payout recipient — a crypto wallet or a bank account.

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How money moves

All asset conversions go through the quote-then-execute pattern. Once you hold the right asset, you pay out to a beneficiary.
1

Create a quote

Specify the account, source asset, destination asset, and either the amount to sell (fromAmount) or the amount to receive (toAmount). The API returns a locked rate, the exact amounts on both sides, and any spread fee. Quotes are valid for 5 minutes.
2

Execute the quote

Call the execute endpoint. Balances update atomically — the source asset is debited and the destination asset is credited in a single operation. The result is a trade transaction.
3

Pay out

Send funds to a pre-registered beneficiary. Crypto payouts complete immediately with an on-chain txHash. Fiat payouts enter LOCKED status and settle via banking rails.

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Environments

EnvironmentBase URLPurpose
Sandboxhttps://api.sandbox.nxos.ioTesting and integration. No real funds.
Productionhttps://api.nxos.ioLive transactions with real funds.
Both environments share the same API surface. Sandbox accounts are provisioned automatically when you sign up.

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Quick example

curl https://api.sandbox.nxos.io/v1/accounts \
  -H "Authorization: Bearer nxos_sk_test_..."

{
  "object": "list",
  "data": [
    {
      "object": "account",
      "accountId": "acct_a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4",
      "name": "Main",
      "isPrimary": true,
      "status": "ACTIVE",
      "fundingMethods": [],
      "createdAt": "2025-01-15T10:30:00.000Z",
      "updatedAt": "2025-01-15T10:30:00.000Z"
    }
  ],
  "hasMore": false,
  "nextCursor": null
}