I have been using the @0x/contract-wrappers to sign a limit order as the taker but I can't find a way to configure a provider that can accept a private key to sign the order rather than using Metamask through the browser. Does anybody have any advice on how to "take" a limit order using a headless server?

2 Answers 2


You don't have to sign anything to take/fill a limit order. As a taker, you pass in the order and the signature (both created by the maker) to fillLimitOrder() on the Exchange Proxy.

Signing transactions with a private key depends on what library you're using. If you are using 0x providers, you can use the PrivateKeyWalletSuprovider as part of a Web3ProviderEngine. If you're using ethers, create a Wallet signer with the private key. If you're using web3js you can call web3.eth.accounts.wallet.add()`.

  • Hi Lawrence. Thanks for taking the time to reply. This is the code I was following: const exchange = new ContractWrappers.IZeroExContract( addresses.exchangeProxy, supportedProvider ); const tx = await exchange .fillLimitOrder(order, signature, new BigNumber(order.takerAmount)) .callAsync(); } In the example the supportedProvider is Metamask. I have been using ethers.js Wallet to sign transactions, but this doesn't seem to be the correct type to pass in as a supportProvider. I will look into the PrivateKeyWallerSubprovider if that is the way to go.
    – DangarStu
    Jan 20, 2022 at 23:04

Edit: The following guide is only for “making” orders, not “taking” orders. Apologies for the confusion.

This gist is a guide on how to create, hash, sign, fill, get state, and cancel a 0x v4 RFQ order. Note that the method of signing an order is the same for limit orders (/orderbook) and RFQ orders (/swap), just the payload is different: https://gist.github.com/PirosB3/8141b51fbb307bca265866ef1cef564f

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