In October 2008, Nakamoto published a paper[6][7] on The Cryptography Mailing list at metzdowd.com[8] describing the bitcoin digital currency. It was titled Bitcoin: A Peer-to-Peer Electronic Cash System. In January 2009, Nakamoto released the first bitcoin software that launched the network and the first units of the bitcoin cryptocurrency, called bitcoins.[9][10] Satoshi Nakamoto released the bitcoin software on Sourceforge on 9 January 2009. Version 0.1 was compiled using Microsoft Visual Studio.

Nakamoto claimed that work on the writing of the code began in 2007.[11] The inventor of bitcoin knew that due to its nature the core design would have to be able to support a broad range of transaction types. The implemented solution enabled specialised codes and data fields from the start through the use of a predicative script.[12]

Nakamoto created a website with the domain name bitcoin.org and continued to collaborate with other developers on the bitcoin software until mid-2010. Around this time, he handed over control of the source code repository and network alert key to Gavin Andresen,[13] transferred several related domains to various prominent members of the bitcoin community, and stopped his involvement in the project. Until shortly before his absence and handover, Nakamoto made all modifications to the source code himself.

The inventor left a text message in the first mined block which reads 'The Times 03/Jan/2009 Chancellor on brink of second bailout for banks'. The text refers to a headline in The Times published on 3 January 2009. It is a strong indication that the first block was mined no earlier than this date.[14] The genesis block has a timestamp of 18:15:05 GMT on January 3 2009. This block is unlike all other blocks in that it doesn't have previous block to reference.[14] This required the use of custom code to mine it. Timestamps for subsequent blocks indicate that Nakamoto did not try to mine all the early blocks solely for themselves in an effort to benefit from a Ponzi scheme.[14]

As the sole, predominant early miner the inventor was awarded bitcoin at genesis and for 10 days afterwards.[15] Except for test transactions these remain unspent since mid January 2009.[15] The public bitcoin transaction log shows that Nakamoto's known addresses contain roughly one million bitcoins.[5] As of 7 February 2017, this is the equivalent of over US$1 billion.[16]