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Ethereum Swift API with support for smart contracts, ENS & ERC20
C Swift C++ Other
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Latest commit 904335d Sep 10, 2019

web3.swift: Ethereum API for Swift



Add web3.swift to your Podfile:

pod 'web3.swift'

Then run the following command:

$ pod install


Getting Started

Create an instance of EthereumAccount with a EthereumKeyStorage provider. This provides a wrapper around your key for web3.swift to use. NOTE We recommend you implement your own KeyStorage provider, instead of relying on the provided EthereumKeyLocalStorage class. This is provided as an example for conformity to the EthereumKeyStorageProtocol.

import web3

let keyStorage = EthereumKeyLocalStorage()
let account = try? EthereumAccount.create(keyStorage: keyStorage, keystorePassword: "MY_PASSWORD")

Create an instance of EthereumClient. This will then provide you access to a set of functions for interacting with the Blockchain.

guard let clientUrl = URL("") else { return }
let client = EthereumClient(url: clientUrl)

You can then interact with the client methods, such as to get the current gas price:

client.eth_getPrice { (error, currentPrice) in
    print("The current gas price is \(currentPrice)")

For more advanced use, you will find support for smart contract parsing. This can be from an ABI JSON definition (e.g. ENS), or by creating strictly typed functions and responses (e.g. ERC20 and ERC721).

Running Tests

The tests will all pass when running against Ropsten. You will need to provide a URL for the blockchain proxy (e.g. on Infura), and a key-pair in TestConfig.swift. Some of the account signing tests will fail, given the signature assertions are against a specific (unprovided) key.


We built web3.swift to be as lightweight as possible. However, given the cryptographic nature of Ethereum, there's a couple of reliable C libraries you will find packaged with this framework:

  • keccac-tiny: An implementation of the FIPS-202-defined SHA-3 and SHAKE functions in 120 cloc (156 lines).
  • secp256k1: For EC operations on curve secp256k1.
  • Tiny AES: A small and portable implementation of the AES ECB, CTR and CBC encryption algorithms.

We also use Apple's own CommonCrypto (via this method) and BigInt via CocoaPod dependency.


There are some features that have yet to be fully implemented! Not every RPC method is currently supported, and here's some other suggestions we would like to see in the future:

  • ABI encoding support for tuples
  • Batch support for JSONRPC interface
  • Use a Hex struct for values to be more explicit in expected types
  • Use Truffle for running tests
  • Add support for Swift Package Manager
  • Bloom Filter support
  • Full ERC20 token support of totalSupply, allowance, transfer, approve, transferFrom, and Transfer/Approval events


The initial project was crafted by the team at Argent. However, we encourage anyone to help implement new features and to keep this library up-to-date. For features and fixes, simply submit a pull request to the develop branch. Please follow the contributing guidelines.

For bug reports and feature requests, please open an issue.


Released under the MIT license.

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