{"id":18571,"date":"2026-03-23T07:59:40","date_gmt":"2026-03-23T07:59:40","guid":{"rendered":"https:\/\/cryptoted.net\/index.php\/2026\/03\/23\/byzantium-hf-announcement-ethereum-foundation-blog\/"},"modified":"2026-03-23T07:59:40","modified_gmt":"2026-03-23T07:59:40","slug":"byzantium-hf-announcement-ethereum-foundation-blog","status":"publish","type":"post","link":"https:\/\/cryptoted.net\/index.php\/2026\/03\/23\/byzantium-hf-announcement-ethereum-foundation-blog\/","title":{"rendered":"Byzantium HF Announcement | Ethereum Foundation Blog"},"content":{"rendered":"


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The Ethereum network will be undergoing a planned hard fork at\u00a0block number 4.37mil (4,370,000)<\/strong>, which will likely occur between 12:00 UTC and 13:00 UTC on\u00a0Monday, October 16, 2017<\/strong>. The Ropsten test network underwent a hard fork on September 19th (UTC) at block number 1.7mil (1,700,000). A countdown timer can be seen at\u00a0https:\/\/fork.codetract.io\/<\/a>.<\/p>\n

<\/g><\/svg><\/a>As a user, what do I need to do?<\/h2>\n

Download the latest version of your Ethereum client:<\/p>\n

<\/g><\/svg><\/a>What if I am using a web or mobile Ethereum wallet like MyEtherWallet or Jaxx?<\/h2>\n

Ethereum websites and mobile applications that allow you to store ether and\/or make transactions are running their own Ethereum client infrastructure to facilitate their services. If you use a third-party web-based or mobile Ethereum wallet, your wallet provider may need to update for the hard fork. It is recommended that you check with them to see what actions they are taking to update for the hard fork and if they are asking their users to take other steps.<\/p>\n

<\/g><\/svg><\/a>What is a hard fork in Ethereum?<\/h2>\n

A hard fork is a change to the underlying Ethereum protocol, creating new rules to improve the system. The protocol changes are activated at a specific block number. All Ethereum clients need to upgrade, otherwise they will be stuck on an incompatible chain following the old rules.<\/p>\n

<\/g><\/svg><\/a>What happens if I do not participate in the hard fork?<\/h2>\n

If you are using an Ethereum client that is not updated for the upcoming hard fork, your client will sync to the pre-fork blockchain once the fork occurs. You will be stuck on an incompatible chain following the old rules, without replay protection against the main network. Old clients will be able to construct transactions, but will not be able to see the effects of those transactions.<\/p>\n

<\/g><\/svg><\/a>What is Metropolis, Byzantium, and Constantinople?<\/h2>\n

Metropolis is a planned Ethereum development phase that includes two hard forks: Byzantium and Constantinople. Byzantium is occurring at block number 4.37mil. Constantinople does not currently have a release date, but is expected in 2018.<\/p>\n

<\/g><\/svg><\/a>What changes are included in the Byzantium hard fork?<\/h2>\n

The following upgrades are included:<\/p>\n