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 is available under open source licenses (e.g., LGPL v3.0), free to download and use for any purpose. Open source means more than simply free to use, though. 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.