Open-source software is a type of software that has its source code released and available to study, change and distribute freely. Some famous examples of open-source software are the Linux operating systems, Mozilla Firefox, Wikipedia and many others. Open-source development is widely used in blockchain projects. Bitcoin’s open-source code became a role model for future generations of digital money. Most of the major cryptocurrencies, such as Litecoin and Ethereum, have open-source code. Open-source projects are also popular in blockchain-related products like open-source wallets and blockchain explorers. Open-source projects have an increased development speed since anyone interested in the product can add some useful extensions and promote those products to a wider audience.