Ethereum Clients

An Ethereum client is a software application that implements the Ethereum specification and communicates over the peer-to-peer network with other Ethereum clients. Different Ethereum clients interoperate if they comply with the reference specification and the standardized communications protocols. While these different clients are implemented by different teams and in different programming languages, they all "speak" the same protocol and follow the same rules. As such, they can all be used to operate and interact with the same Ethereum network.

Ethereum is an open source project and the source code for all the major clients are available under open source licenses (e.g. LGPL v3.0), so they are free to download and use for any purpose. Open source means more than simply free to use. It also means that Ethereum is developed by an open community of volunteers and can be modified by anyone. More eyes means more trustworthy code.

Ethereum is defined by a formal specification called the "Yellow Paper" (see [references]).

This is in contrast to, for example, Bitcoin, which is not defined in any formal way. Where Bitcoin’s "specification" is the reference implementation Bitcoin Core, Ethereum’s specification is documented in a paper that combines an English and a mathematical (formal) specification. This formal specification, in addition to various Ethereum Improvement Proposals, defines the standard behavior of an Ethereum client. The Yellow Paper is periodically updated as major changes are made to Ethereum.

As a result of Ethereum’s clear formal specification, there are a number of independently developed, yet interoperable, software implementations of an Ethereum client. Ethereum has a greater diversity of implementations running on the network than any other blockchain, which is generally regarded as a good thing. Indeed, it has, for example, proven itself to be an excellent way of defending against attacks on the network, because exploitation of a particular client’s implementation strategy simply hassles the developers while they patch the exploit, while other clients keep the network running almost unaffected.

Ethereum Networks

There exist a variety of Ethereum-based networks which largely conform to the formal specification defined in the Ethereum "Yellow Paper," but which may or may not interoperate with each other.

Among these Ethereum-based networks are: Ethereum, Ethereum Classic, Ella, Expanse, Ubiq, Musicoin, and many others. While mostly compatible at the protocol level, these networks often have features or attributes that require maintainers of Ethereum client software to make small changes in order to support each network. Because of this, not every version of Ethereum client software runs every Ethereum-based blockchain.

Currently, there are six main implementations of the Ethereum protocol, written in six different languages:

  • Parity, written in Rust

  • Geth, written in Go

  • cpp-ethereum, written in C++

  • pyethereum, written in Python

  • Mantis, written in Scala,

  • and Harmony, written in Java.

In this section, we will look at the two most common clients, Parity and Geth. We’ll learn how to set up a node using each client, and explore some of their command-line and application programming interfaces (APIs).

Should I run a full node?

The health, resilience, and censorship resistance of blockchains depend on having many independently operated and geographically dispersed full nodes. Each full node can help other new nodes obtain the block data to bootstrap their operation, as well as offer the operator an authoritative and independent verification of all transactions and contracts.

However, running a full node will incur a cost in hardware resources and bandwidth. A full node must download more than 80GB of data (as of April 2018; depending on client) and store it on a local hard drive. This data burden increases quite rapidly every day as new transactions and blocks are added. We discuss this topic in greater detail in Hardware Requirements for a Full Node.

A full node running on a live mainnet network is not necessary for Ethereum development. You can do almost everything you need to do with a testnet node (which connects you to one of the smaller public test blockchains), with a local private blockchain like Ganache, or with a cloud-based Ethereum client offered by a service provider like Infura.

You also have the option of running a remote client, which does not store a local copy of the blockchain or validate blocks and transactions. These clients offer the functionality of a wallet and can create and broadcast transactions. Remote clients can be used to connect to existing networks, such as your own full node, a public blockchain, a public or permissioned (Proof-of-Authority) testnet, or a private local blockchain. In practice, you will likely use a remote client such as MetaMask, Emerald Wallet, MyEtherWallet or MyCrypto as a convenient way to switch between all of the different node options.

The terms "remote client" and "wallet" are used interchangeably, though there are some differences. Usually, a remote client offers an API (such as the web3.js API) in addition to the transaction functionality of a wallet.

Do not confuse the concept of a remote wallet in Ethereum with that of a light client (which is analogous to a Simplified Payment Verification client in Bitcoin). Light clients validate block headers and use Merkle proofs to validate the inclusion of transactions in the blockchain and determine their effects, giving them a similar level of security to a full node. Conversely, Ethereum remote clients do not validate block headers or transactions. They entirely trust a full client to give them access to the blockchain, and hence lose significant security and anonymity guarantees. You can mitigate these problems by using a full client you run yourself.

Full Node Advantages and Disadvantages

Choosing to run a full node helps with the operation of the networks you connect it to, but also incurs some mild to moderate costs for you. Let’s look at some of the advantages and disadvantages.


  • Supports the resilience and censorship resistance of Ethereum-based networks.

  • Authoritatively validates all transactions.

  • Can interact with any contract on the public blockchain without an intermediary.

  • Can directly deploy contracts into the public blockchain without an intermediary.

  • Can query (read-only) the blockchain status (accounts, contracts, etc.) offline.

  • Can query the blockchain without letting a third party know the information you’re reading.


  • Requires significant and growing hardware and bandwidth resources.

  • May require several days to fully sync when first started.

  • Must be maintained, upgraded and kept online to remain synced.

Public Testnet Advantages and Disadvantages

Whether or not you choose to run a full node, you will probably want to run a public testnet node. Let’s look at some of the advantages and disadvantages of using a public testnet.


  • A testnet node needs to sync and store much less data, ~10GB depending on the network (as of April 2018).

  • A testnet node can sync fully in a few hours.

  • Deploying contracts or making transactions requires test ether, which has no value and can be acquired for free from several "faucets".

  • Testnets are public blockchains with many other users and contracts, running "live".


  • You can’t use "real" money on a testnet; it runs on test ether. Consequently, you can’t test security against real adversaries, as there is nothing at stake.

  • There are some aspects of a public blockchain that you cannot test realistically on testnet. For example, transaction fees, although necessary to send transactions, are not a consideration on testnet, since gas is free. Further, the testnets do not experience network congestion like the public mainnet sometimes does.

Local Blockchain Simulation Advantages and Disadvantages

For many testing purposes, the best option is to launch a single-instance private blockchain. Ganache (formerly named testrpc)is one of the most popular local blockchain simulations that you can interact with, without any other participants. It shares many of the advantages and disadvantages of the public testnet, but also has some differences.


  • No syncing and almost no data on disk. You mine the first block yourself.

  • No need to obtain test ether: you "award" yourself mining rewards that you can use for testing.

  • No other users, just you.

  • No other contracts, just the ones you deploy after you launch it.


  • Having no other users means that it doesn’t behave the same as a public blockchain. There’s no competition for transaction space or sequencing of transactions.

  • No miners other than you means that mining is more predictable, therefore you can’t test some scenarios that occur on a public blockchain.

  • Having no other contracts means you have to deploy everything that you want to test, including dependencies and contract libraries.

  • You can’t recreate some of the public contracts and their addresses to test some scenarios (e.g. the DAO contract).

Running an Ethereum client

If you have the time and resources, you should attempt to run a full node, even if only to learn more about the process. In the next few sections we will download, compile, and run the Ethereum clients Parity and Geth. This requires some familiarity with using the command-line interface on your operating system. It’s worth installing these clients, whether you choose to run them as full nodes, as testnet nodes, or as clients to a local private blockchain.

Hardware Requirements for a Full Node

Before we get started, you should ensure you have a computer with sufficient resources to run an Ethereum full node. You will need at least 80GB of disk space to store a full copy of the Ethereum blockchain. If you also want to run a full node on the Ethereum testnet, you will need at least an additional 15GB. Downloading 80GB of blockchain data can take a long time, so it’s recommended that you work on a fast Internet connection.

Syncing the Ethereum blockchain is very input-output (I/O) intensive. It is best to have a Solid-State Drive (SSD). If you have a mechanical hard disk drive (HDD), you will need at least 8GB of RAM to use as cache. Otherwise, you may discover that your system is too slow to keep up and sync fully.

Minimum Requirements:

  • CPU with 2+ cores.

  • At least 80GB free storage space.

  • 4GB RAM minimum with a SSD, 8GB+ if you have an HDD.

  • 8 MBit/sec download Internet service.

These are the minimum requirements to sync a full (but pruned) copy of an Ethereum-based blockchain.

At the time of writing (April 2018) the Parity codebase is lighter on resources, so if you’re running with limited hardware you’ll likely see better results using Parity.

If you want to sync in a reasonable amount of time and store all the development tools, libraries, clients, and blockchains we discuss in this book, you will want a more capable computer.

Recommended Specifications:

  • Fast CPU with 4+ cores.

  • 16GB+ RAM.

  • Fast SSD with at least 500GB free space.

  • 25+ MBit/sec download Internet service.

It’s difficult to predict how fast a blockchain’s size will increase and when more disk space will be required, so it’s recommended to check the blockchain’s latest size before you start syncing.


The disk size requirements above assume you will be running a node with default settings, where the blockchain is "pruned" of old state data. If you instead run a full "archival" node, where all state is kept on disk, it will likely require more than 1TB of disk space.

Software Requirements for Building and Running a Client (Node)

This section covers Parity and Geth client software. It also assumes you are using a Unix-like command-line environment. The examples show the commands and output as they appear on an Ubuntu GNU/Linux operating system running the Bash shell (command-line execution environment).

Typically every blockchain will have their own version of Geth, while Parity provides support for multiple Ethereum-based blockchains (Ethereum, Ethereum Classic, Ellaism, Expanse, Musicoin) with the same client download.


In many of the examples in this chapter, we will be using the operating system’s command-line interface (also known as a "shell"), accessed via a "terminal" application. The shell will display a prompt; you type a command, and the shell responds with some text and a new prompt for your next command. The prompt may look different on your system, but in the following examples, it is denoted by a $ symbol. In the examples, when you see text after a $ symbol, don’t type the $ symbol but type the command immediately following it, then press Enter to execute the command. In the examples, the lines below each command are the operating system’s responses to that command. When you see the next $ prefix, you’ll know it’s a new command and you should repeat the process.

Before we get started, you need to check some software is installed. If you’ve never done any software development on the computer you are currently using, you will probably need to install some basic tools. For the examples that follow, you will need to install git, the source-code management system; golang, the Go programming language and standard libraries; and Rust, a systems programming language.

Git can be installed by following the instructions here:

Go can be installed by following the instructions here:


Geth requirements vary, but if you stick with Go version 1.10 or greater you should be able to compile any version of Geth you want. Of course, you should always refer to the documentation for your chosen flavor of Geth.

The version of golang that is installed on your operating system or is available from your system’s package manager may be significantly older than 1.10. If so, remove it and install the latest version from

Rust can be installed by following the instructions here:


Parity requires Rust version 1.27 or greater.

Parity also requires some software libraries, such as OpenSSL and libudev. To install these on a Ubuntu or Debian GNU/Linux compatible system:

$ sudo apt-get install openssl libssl-dev libudev-dev cmake

For other operating systems, use the package manager of your OS or follow the Wiki instructions ( to install the required libraries.

Now you have git, golang, rust, and necessary libraries installed, let’s get to work!


Parity is an implementation of a full node Ethereum client and DApp browser. Parity was written from the "ground up" in Rust, a systems programming language, with the aim of building a modular, secure, and scalable Ethereum client. Parity is developed by Parity Tech, a UK company, and is released under the GPLv3 free software license.


Disclosure: One of the authors of this book, Gavin Wood, is the founder of Parity Tech and wrote much of the Parity client. Parity represents about 25% of the installed Ethereum client base.

To install Parity, you can use the Rust package manager cargo or download the source code from GitHub. The package manager also downloads the source code, so there’s not much difference between the two options. In the next section, we will show you how to download and compile Parity yourself.

Installing Parity

The Parity Wiki offers instructions for building Parity in different environments and containers:

We’ll build Parity from source. This assumes you have already installed Rust using rustup (See Software Requirements for Building and Running a Client (Node)).

First, let’s get the source code from GitHub:

$ git clone

Now, let’s change to the parity directory and use cargo to build the executable:

$ cd parity
$ cargo install

If all goes well, you should see something like:

$ cargo install
    Updating git repository ``
 Downloading log v0.3.7
 Downloading isatty v0.1.1
 Downloading regex v0.2.1


Compiling parity-ipfs-api v1.7.0
Compiling parity-rpc v1.7.0
Compiling parity-rpc-client v1.4.0
Compiling rpc-cli v1.4.0 (file:///home/aantonop/Dev/parity/rpc_cli)
Finished dev [unoptimized + debuginfo] target(s) in 479.12 secs

Let’s try and run parity to see if it is installed, by invoking the --version option:

$ parity --version
  version Parity/v1.7.0-unstable-02edc95-20170623/x86_64-linux-gnu/rustc1.18.0
Copyright 2015, 2016, 2017 Parity Technologies (UK) Ltd
License GPLv3+: GNU GPL version 3 or later <>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

By Wood/Paronyan/Kotewicz/Drwięga/Volf

Great! Now that Parity is installed, we can sync the blockchain and get started with some basic command-line options.

Go-Ethereum (Geth)

Geth is the Go language implementation, which is actively developed by the Ethereum Foundation, so is considered the "official" implementation of the Ethereum client. Typically, every Ethereum-based blockchain will have its own Geth implementation. If you’re running Geth, then you’ll want to make sure you grab the correct version for your blockchain using one of the repository links below.


You can also skip these instructions and install a precompiled binary for your platform of choice. The precompiled releases are much easier to install and can be found at the "release" section of the repositories above. However, you may learn more by downloading and compiling the software yourself.

Cloning the repository

Our first step is to clone the git repository, to get a copy of the source code.

To make a local clone of this repository, use the git command as follows, in your home directory or under any directory you use for development:

$ git clone <Repository Link>

You should see a progress report as the repository is copied to your local system:

Cloning into 'go-ethereum'...
remote: Counting objects: 62587, done.
remote: Compressing objects: 100% (26/26), done.
remote: Total 62587 (delta 10), reused 13 (delta 4), pack-reused 62557
Receiving objects: 100% (62587/62587), 84.51 MiB | 1.40 MiB/s, done.
Resolving deltas: 100% (41554/41554), done.
Checking connectivity... done.

Great! Now that we have a local copy of Geth, we can compile an executable for our platform.

Building Geth from Source Code

To build Geth, change to the directory where the source code was downloaded and use the make command:

$ cd go-ethereum
$ make geth

If all goes well, you will see the Go compiler building each component until it produces the geth executable:

build/ go run build/ci.go install ./cmd/geth
>>> /usr/local/go/bin/go install -ldflags -X main.gitCommit=58a1e13e6dd7f52a1d5e67bee47d23fd6cfdee5c -v ./cmd/geth
Done building.
Run "build/bin/geth" to launch geth.

Let’s make sure geth works without actually starting it running:

$ ./build/bin/geth version

Version: 1.6.6-unstable
Git Commit: 58a1e13e6dd7f52a1d5e67bee47d23fd6cfdee5c
Architecture: amd64
Protocol Versions: [63 62]
Network Id: 1
Go Version: go1.8.3
Operating System: linux

Your geth version command may show slightly different information, but you should see a version report much like the one above.

Don’t start running geth yet, because it will start synchronizing the blockchain "the slow way" and that will take far too long (weeks). The First Synchronization of Ethereum-based Blockchains explains the challenge with the initial synchronization of Ethereum’s blockchain.

The First Synchronization of Ethereum-based Blockchains

Normally, when syncing an Ethereum blockchain, your client will download and validate every block and every transaction since the very start, i.e. from the genesis block.

While it is possible to fully sync the blockchain this way, the sync will take a very long time and has high resource requirements (it will need much more RAM, and will take a very long time indeed if you don’t have fast storage).

Many Ethereum-based blockchains were the victim of a Denial of Service (DoS) attack at the end of 2016. Blockchains affected by this attack will tend to sync slowly when doing a full sync.

For example, on Ethereum, a new client will make rapid progress until it reaches block 2,283,397. This block was mined on 2016/09/18 and marks the beginning of the DoS attacks. From this block to block 2,700,031 (2016/11/26), the validation of transactions becomes extremely slow, memory intensive, and I/O intensive. This results in validation times exceeding 1 minute per block. Ethereum implemented a series of upgrades, using hard forks, to address the underlying vulnerabilities that were exploited in the denial of service attacks. These upgrades also cleaned up the blockchain by removing some 20 million empty accounts created by spam transactions.

If you are syncing with full validation, your client will slow down and may take several days, or perhaps even longer, to validate the blocks affected by this DoS attack.

Fortunately, most Ethereum clients include an option to perform a "fast" synchronization that skips the full validation of transactions until it has synced to the tip of the blockchain, then resumes full validation.

For Geth, the option to enable fast synchronization is typically called --fast. You may need to refer to the specific instructions for your chosen Ethereum chain.

Parity does fast synchronization by default.


Geth can only operate fast synchronization when starting with an empty block database. If you have already started syncing without "fast" mode, Geth cannot switch. It is faster to delete the blockchain data directory and start "fast" syncing from the beginning than to continue syncing with full validation. Be careful to not delete any wallets when deleting the blockchain data!

Running geth or parity

Now that you’ve understood the challenges of the "first sync", we’re ready to start an Ethereum client and sync the blockchain. For both geth and parity, you can use the --help option to see all the configuration parameters. Other than using --fast for geth as outlined in The First Synchronization of Ethereum-based Blockchains, the default settings are usually sensible and appropriate for most uses. Choose how to configure any optional parameters to suit your needs, then start geth or parity to sync the chain. Then wait…​


Syncing the Ethereum blockchain will take anywhere from half a day on a very fast system with lots of RAM, to several days on a slower system.

JSON-RPC Interface

Ethereum clients offer an Application Programming Interface (API) and a set of Remote Procedure Call (RPC) commands, which are encoded as JavaScript Object Notation (JSON). You will see this referred to as the JSON-RPC API. Essentially, the JSON-RPC API is an interface that allows us to write programs that use an Ethereum client as a gateway to an Ethereum network and blockchain.

Usually, the RPC interface is offered over as an HTTP service on port 8545. For security reasons it is restricted, by default, to only accept connections from localhost (the IP address of your own computer which is

To access the JSON-RPC API, you can use a specialized library, written in the programming language of your choice, which provides "stub" function calls corresponding to each available RPC command. Or, you can manually construct HTTP requests and send/receive JSON encoded requests. You can even use a generic command-line HTTP client, like curl, to call the RPC interface. Let’s try that. First, ensure that you have Geth configured and running, then switch to a new terminal window (e.g. with <Ctrl>+<Shift>+N or <Ctrl>+<Shift>+T in an existing terminal window) as shown in Using curl to call the web3_clientVersion function over JSON-RPC:

Using curl to call the web3_clientVersion function over JSON-RPC
$ curl -X POST -H "Content-Type: application/json" --data \
'{"jsonrpc":"2.0","method":"web3_clientVersion","params":[],"id":1}' \


In this example, we use curl to make an HTTP connection to address http://localhost:8545. We are already running geth, which offers the JSON-RPC API as an HTTP service on port 8545. We instruct curl to use the HTTP POST command and to identify the content as Content-Type: application/json. Finally, we pass a JSON-encoded request as the data component of our HTTP request. Most of our command line is just setting up curl to make the HTTP connection correctly. The interesting part is the actual JSON-RPC command we issue:


The JSON-RPC request is formatted according to the JSON-RPC 2.0 specification, which you can see here:

Each request contains 4 elements:


Version of the JSON-RPC protocol. This MUST be exactly "2.0".


The name of the method to be invoked.


A structured value that holds the parameter values to be used during the invocation of the method. This member MAY be omitted.


An identifier established by the Client that MUST contain a String, Number, or NULL value if included. The Server MUST reply with the same value in the Response object if included. This member is used to correlate the context between the two objects.


The id parameter is used primarily when you are making multiple requests in a single JSON-RPC call, a practice called batching. Batching is used to avoid the overhead of a new HTTP and TCP connection for every request. In the Ethereum context for example, we would use batching if we wanted to retrieve thousands of transactions in one HTTP connection. When batching, you set a different id for each request and then match it to the id in each response from the JSON-RPC server. The easiest way to implement this is to maintain a counter and increment the value for each request.

The response we receive is:


This tells us that the JSON-RPC API is being served by Geth client version 1.8.0.

Let’s try something a bit more interesting. In the next example, we ask the JSON-RPC API for the current price of gas in wei:

$ curl -X POST -H "Content-Type: application/json" --data \
'{"jsonrpc":"2.0","method":"eth_gasPrice","params":[],"id":4213}' \


The response, 0x430e23400, tells us that the current gas price is 1.8 Gwei (gigawei or billion wei). If, like me, you don’t think in hexadecimal, you can convert it to decimal on the command line with a little bash-fu:

$ echo $((0x430e23400))


The full JSON-RPC API can be investigated on the Ethereum wiki:

Parity’s Geth Compatibility Mode

Parity has a special "Geth Compatibility Mode", where it offers a JSON-RPC API that is identical to that offered by geth. To run Parity in Geth Compatibility Mode, use the --geth switch:

$ parity --geth

Remote Ethereum Clients

Remote clients offer a subset of the functionality of a full client. They do not store the full Ethereum blockchain, so they are faster to set up and require far less data storage.

A remote client offers one or more of the following functions:

  • Manage private keys and Ethereum addresses in a wallet.

  • Create, sign, and broadcast transactions.

  • Interact with smart contracts, using the data payload.

  • Browse and interact with DApps.

  • Offer links to external services such as block explorers.

  • Convert ether units and retrieve exchange rates from external sources.

  • Inject a web3 instance into the web browser as a JavaScript object.

  • Use a web3 instance provided/injected into the browser by another client.

  • Access RPC services on a local or remote Ethereum node.

Some remote clients, for example mobile (smartphone) wallets, offer only basic wallet functionality. Other remote clients are full-blown DApp browsers. Remote clients commonly offer some of the functions of a full node Ethereum client without synchronizing a local copy of the Ethereum blockchain by connecting to a full node being run elsewhere, e.g. by you locally on your machine or on a web server, or by a third party on their servers.

Let’s look at some of the most popular remote clients and the functions they offer.

Mobile (Smartphone) Wallets

All mobile wallets are remote clients, because smartphones do not have adequate resources to run a full Ethereum client. Light clients are in development and not in general use for Ethereum. In the case of Parity, it is marked "experimental" and can be used by running parity with the --light option.

Popular mobile wallets include Jaxx, Status, and Trust Wallet. We list these as examples of popular mobile wallets (this is not an endorsement or an indication of the security or functionality of these wallets).


A multi-currency mobile wallet based on BIP39 mnemonic seeds, with support for Bitcoin, Litecoin, Ethereum, Ethereum Classic, ZCash, a variety of ERC20 tokens, and many other currencies. Jaxx is available on Android, iOS, as a browser plugin wallet, and as a desktop wallet for a variety of operating systems. Find it at


A mobile wallet and DApp browser, with support for a variety of tokens and popular DApps. Available for iOS and Android. Find it at

Trust Wallet

A mobile Ethereum and Ethereum Classic wallet that supports ERC20 and ERC223 tokens. Trust Wallet is available for iOS and Android. Find it at

Cipher Browser

A full-featured Ethereum-enabled mobile DApp browser and wallet. Allows integration with Ethereum apps and tokens. Available for iOS and Android. Find it at

Browser wallets

A variety of wallets and DApp browsers are available as plugins or extensions of web browsers such as Chrome and Firefox. These are remote clients that run inside your browser.

Some of the more popular ones are MetaMask, Jaxx, and MyEtherWallet/MyCrypto.


MetaMask was introduced in [intro_chapter], and is a versatile browser-based wallet, RPC client, and basic contract explorer. It is available on Chrome, Firefox, Opera, and Brave Browser. Find MetaMask at

At first glance, MetaMask is a browser-based wallet. But, unlike other browser wallets, MetaMask injects a web3 instance into the browser, acting as an RPC client that connects to a variety of Ethereum blockchains (mainnet, Ropsten testnet, Kovan testnet, local RPC node, etc.). The ability to inject a web3 instance and act as a gateway to external RPC services makes MetaMask a very powerful tool for developers and users alike. It can be combined, for example, with MyEtherWallet or MyCrypto, acting as an web3 provider and RPC gateway for those tools.


Jaxx, which was introduced as a mobile wallet in Mobile (Smartphone) Wallets, is also available as a Chrome and Firefox extension, and as a desktop wallet. Find it at

MyEtherWallet (MEW)

MyEtherWallet is a browser-based JavaScript remote client that offers:

  • A software wallet running in JavaScript.

  • A bridge to popular hardware wallets such as the Trezor and Ledger.

  • A web3 interface that can connect to a web3 instance injected by another client (e.g. MetaMask).

  • An RPC client that can connect to an Ethereum full client.

  • A basic interface that can interact with smart contracts, given a contract’s address and Application Binary Interface (ABI).

MyEtherWallet is very useful for testing and as an interface to hardware wallets. It should not be used as a primary software wallet, as it is exposed to threats via the browser environment and is not a secure key storage system.

You must be very careful when accessing MyEtherWallet and other browser-based JavaScript wallets, as they are frequent targets for phishing. Always use a bookmark and not a search engine or link to access the correct web URL. MyEtherWallet can be found at


Just prior to publication of the first edition of this book, the MyEtherWallet project split into two competing implementations, guided by two independent development teams: a "fork", as it is called in open source development. The two projects are called MyEtherWallet (the original branding) and MyCrypto. At the time of the split, MyCrypto offered identical functionality as MyEtherWallet. It is likely that the two projects will diverge as the two development teams adopt different goals and priorities.

As with MyEtherWallet, you must be very careful when accessing MyCrypto in your browser. Always use a bookmark, or type the URL very carefully (then bookmark it for future use).

MyCrypto can be found at


Mist was the first Ethereum-enabled browser, built by the Ethereum Foundation. It also contains a browser-based wallet that was the first implementation of the ERC20 token standard (Fabian Vogelsteller, author of ERC20 was also the main developer of Mist). Mist was also the first wallet to introduce the camelCase checksum (EIP-155). Mist runs a full node, and offers a full DApp browser with support for Swarm based storage and ENS addresses. Find it at