Quickstart: Raw API (cURL)

This guide walks you through placing an order on CoW Protocol using nothing but cURL and the REST API. No SDK, no framework — just raw HTTP requests against the Sepolia testnet. By the end you will have:

Fetched a quote
Signed an order
Submitted it to the order book
Monitored it until settlement

Prerequisites

Before you start, make sure you have:

cURL installed (ships with macOS and most Linux distributions)
An Ethereum wallet with some WETH on the Sepolia testnet
- Sepolia WETH:
- Sepolia COW (buy token in this guide):
Token approval for the GPv2VaultRelayer contract so it can spend your sell token

You must approve the GPv2VaultRelayer () to spend your sell token before submitting an order. Without this approval the order will revert on settlement.You can do this via Etherscan’s “Write Contract” tab, or with Foundry:

cast send 0xfFf9976782d46CC05630D1f6eBAb18b2324d6B14 \
  "approve(address,uint256)" \
  0xC92E8bdf79f0507f65a392b0ab4667716BFE0110 \
  115792089237316195423570985008687907853269984665640564039457584007913129639935 \
  --rpc-url https://rpc.sepolia.org \
  --private-key $PRIVATE_KEY

All examples in this guide target the Sepolia testnet (). Replace sepolia with mainnet, xdai, arbitrum_one, or base for other networks.

Walkthrough

Before placing orders in production, review the Pre-Flight Checklist to avoid the most common integration mistakes.

Troubleshooting

Common errors you may encounter:

Error	Cause	Fix
`InsufficientBalance`	Your wallet does not hold enough sell token	Fund your wallet with more tokens on Sepolia
`InsufficientAllowance`	The VaultRelayer has not been approved to spend your token	Approve `0xC92E8bdf79f0507f65a392b0ab4667716BFE0110` for the sell token
`InvalidSignature`	The signature does not match the order data or signer	Ensure the EIP-712 domain, types, and order values match exactly
`DuplicatedOrder`	An identical order already exists	Change `validTo` or amounts slightly
`SellAmountDoesNotCoverFee`	The sell amount is too small to cover network costs	Increase your sell amount
`QuoteNotFound` / `NoLiquidity`	No solver can fill this trade pair	Try a different token pair or larger amount

For the full list of API error codes, see the Order Book API Reference.

Next Steps

Now that you know how the raw API works, explore these resources:

TypeScript SDK Quickstart — a more ergonomic experience with TypeScript helpers for signing, quoting, and order management
How Intents Are Formed — deep dive into the fee pipeline and amount stages
Signing Schemes — all four supported signing methods (EIP-712, eth_sign, ERC-1271, PreSign)
Limit Orders — place limit orders through CoW Swap
TWAP Orders — time-weighted average price orders
API Integration Guide — complete step-by-step API reference with fee formulas and pre-flight checklist
Testing Guide — how to test on Sepolia and graduate to production

Last modified on March 17, 2026

Testing Your Integration

Quickstart: Python

Overview

How It Works

Benefits

Order Types

Flash Loans

CoW AMM

CoW Explorer

Integration

Architecture

API Reference

Core Reference

Auctions

Prerequisites

Walkthrough

Troubleshooting

Next Steps

​Prerequisites

​Walkthrough

​Troubleshooting

​Next Steps

Prerequisites

Walkthrough

Troubleshooting

Next Steps