Ethereum’s Four Stages of Development

Ethereum’s development was planned over four distinct stages, with major changes occurring at each stage. A stage may include subreleases, known as “hard forks,” that change functionality in a way that is not backward compatible.

The four main development stages are codenamed Frontier, Homestead, Metropolis, and Serenity. The intermediate hard forks that have occurred (or are planned) to date are codenamed Ice Age, DAO, Tangerine Whistle, Spurious Dragon, Byzantium, and Constantinople. Both the development stages and the intermediate hard forks are shown on the following timeline, which is “dated” by block number:

Block #0

Frontier—The initial stage of Ethereum, lasting from July 30, 2015, to March 2016.

Block #200,000

Ice Age—A hard fork to introduce an exponential difficulty increase, to motivate a transition to PoS when ready.

Block #1,150,000

Homestead—The second stage of Ethereum, launched in March 2016.

Block #1,192,000

DAO—A hard fork that reimbursed victims of the hacked DAO contract and caused Ethereum and Ethereum Classic to split into two competing systems.

Block #2,463,000

Tangerine Whistle—A hard fork to change the gas calculation for certain I/O-heavy operations and to clear the accumulated state from a denial-of-service (DoS) attack that exploited the low gas cost of those operations.

Block #2,675,000

Spurious Dragon—A hard fork to address more DoS attack vectors, and another state clearing. Also, a replay attack protection mechanism.

Block #4,370,000

Metropolis Byzantium—Metropolis is the third stage of Ethereum, current at the time of writing this book, launched in October 2017. Byzantium is the first of two hard forks planned for Metropolis.

After Byzantium, there is one more hard fork planned for Metropolis: Constantinople. Metropolis will be followed by the final stage of Ethereum’s deployment, codenamed Serenity.