Decentralized Applications (DApps) are applications that run across a decentralized network and are not owned or controlled by a centralized authority. They differ from distributed applications primarily in terms of ownership. A distributed application may run on thousands of computers, but those computers and the management of the software running on them are controlled by a central authority—Amazon, Microsoft, and so on. A decentralized application runs on what is typically a peer-to-peer network and is designed in such a way that no one person or organization can control the functioning of the application. A decentralized application does not require a blockchain. There were multiple decentralized applications before blockchain: BitTorrent, Tor, and Mastodon are all decentralized applications that exist without the use of a blockchain.

In this chapter, we are going to cover the following:

• The major features of a decentralized application
• The largest decentralized applications in operation today
• Non-blockchain based decentralized applications

The goal of this chapter is to give you an understanding of decentralized applications and their development, as well as making you aware of ecosystems and code that already exists. If you are interested in building a decentralized application, interoperability with the existing ecosystems out there will greatly improve your odds.

Let's start by taking a look at what makes an application decentralized.