It is assumed the reader of this book may be contemplating launching their own decentralized application project or contributing to an existing one. When building new decentralized applications, it is important to be aware of what already exists so that your application can take advantage of the existing functionality. There are a number of existing decentralized applications that are running and in production and that have already undergone substantial development. In general, these applications provide services to help other decentralized applications flourish. In addition, these applications are all open source. If you evaluate one of these projects and find it is missing something, substantially less effort is likely required to either contribute to or for existing functionality.