1st generation blockchain refers to the early stage of blockchain technology development. It began with the creation of Bitcoin, the first cryptocurrency, in 2009.

In a 1st generation blockchain, transactions are recorded in a chronological and immutable chain of blocks. These blocks contain a list of transactions that are validated by network participants known as miners.

The main feature of 1st generation blockchains is decentralization, meaning that there is no central authority controlling the network. This helps to prevent fraud and manipulation of transactions.

However, 1st generation blockchains are limited in terms of scalability and transaction speed due to their consensus mechanisms, such as Proof of Work. This has led to issues like high transaction fees and slow processing times during peak usage.

Overall, 1st generation blockchains laid the foundation for the development of more advanced blockchain technologies, such as 2nd and 3rd generation blockchains, which aim to address the limitations of earlier versions.