Codex Par | 1:1 USDT ↔ USDC Swaps via API | Codex FX

USDT ↔ USDC swaps. Via API.

Codex Par is a 1:1 stablecoin swap API for payment operators. Offer your customers USDT↔USDC conversion at par with no extra cost for them and fees billed separately to you.

The marketUSDT/USDC

1.001858

+18.6 bps from par

Our API responseLocked

1.000000

Par. Every call. Every size.

POST /v1/swap
{
  "from":     "USDC",
  "to":       "USDT",
  "amount":   "1000000.00",
  "rate":     "1.000000",
  "receive":  "1000000.00"
}

Market rate shown is illustrative.

Backed by:

Dragonfly

Coinbase Ventures

Circle Ventures

Wintermute

Cumberland

In a bank, a dollar is a dollar. Onchain, it isn’t.

USDT and USDC are assets from different issuers, and they trade at a spread. A few basis points in calm markets, far more under stress.

Your customers do not see that. They expect 1,000 USDC when they swap 1,000 USDT, and anything less looks like your mistake.

Codex Par ensures the full amount arrives. Pay a transparent fee instead of holding inventory or absorbing the spread, and keep your 1:1 promise.

53,600

Your customer swaps5630,,660901USDT

↓

Codex Par returns1:1

↓

Your customer receives5835,,610209USDC

How 1:1 swaps work

Codex Par sits behind your product, managing the liquidity and settlement. You keep the customer relationship and the economics, whether your customers convert USDT to USDC or USDC to USDT.

01

Request swap

Call the API endpoint. Every rate returned is 1:1, in both directions. No visible spread or conversion fee for your customers.

POST /v1/swap
{
  “from”:     “USDC”,
  “to”:       “USDT”,
  “amount”:   “1000000.00”,
  “rate”:     “1.000000”,
  “receive”:  “1000000.00”
}

02

Execute swap

Codex Par executes the USDT/USDC swap, 24/7/365, within a defined settlement window. Not a best-effort fill with no guaranteed time.

03

Get billed transparently

Your customers always see 1:1. Your cost is invoiced separately and volume dependent. You always know what you pay, and why.

Invoice

Customer swap

Pay

50,000

USDCReceive

50,000

USDT

Why Codex Par

There are multiple ways to give a customer par on USDT and USDC swaps. Only one of them scales.

Onchain

In-house

Rate

Exactly 1:1.

Varies per trade.

1:1 if you absorb the spread.

Settlement

Defined settlement window, 24/7/365.

No guaranteed time.

Instant, only while inventory lasts.

Liquidity

Institutional, sized for real volume.

Shared pool that thins out under load.

Your balance sheet.

Cost

Invoiced on a transparent, volume-tiered basis.

Market spread, plus uncertain gas and slippage.

Full market spread, locked-up capital, plus your own risk tooling.

Anyone can quote 1:1. Keeping it at scale is the hard part.

Live in production

since early 2026

Hundreds of millions

in monthly volume

Our customers move between USDT and USDC constantly. Codex Par lets us give them a true 1:1 without sourcing liquidity, and the fee is billed separately to us. We integrated it with a single endpoint.

APAC Payment Operator

Head of Product

FAQ

Find answers about how Codex Par works, pricing, supported chains, and more.

  1. What is Codex Par? Codex Par is a 1:1 stablecoin swap API. Payment operators use it to offer their customers USDT ↔ USDC conversion at par, while Codex manages the liquidity and settlement behind the scenes.

  2. Who is Codex Par for? Payment operators with downstream customers moving between USDC and USDT, such as PSPs, wallets, remittance companies, and crypto payment processors.

  3. Is there a fee to swap between USDC and USDT? On the open market, USDT and USDC trade at a spread, plus venue fees or gas. But through Codex Par, your customers pay no fee and see no spread. Every swap executes at exactly 1:1. Your cost as the operator is invoiced separately and volume dependent. You always know what you pay, and why.

  4. Which chains and tokens are supported? USDC on Ethereum, Solana, Polygon, Codex, Base, Optimism, Arbitrum, and Avalanche. USDT on Ethereum, Solana, Tron, and Polygon.

  5. Do our customers need to KYB with Codex? Codex can rely on the KYB you've already performed on your customers. The KYB is subject to periodic sample testing so you can keep the relationship.

  6. Do we need to prefund? No. Codex holds and manages the liquidity for you on both sides so you don't need to.

  7. How do we integrate? One API key, one endpoint. Every rate returned is 1:1, in both directions.