A big upgrade for decentralized app platform Ethereum has gone as planned on Thursday.

After a failed try in January, which was postponed just one day before the scheduled upgrade date due to a security issue, Ethereum has now been upgraded to a new version called Constantinople. Another, smaller upgrade called St. Petersburg, was rolled out as well to mitigate the security issue found in the original Constantinople code.

Constantinople brings a number of improvements to Ethereum's efficiency and speed (read a detailed overview here). But, most importantly, it paves the way for a major future upgrade called Casper. That upgrade, sometimes also called Ethereum 2.0, is scheduled to go live later this year and bring an immensely important switch from proof-of-work to proof-of-stake consensus mechanism, among other changes.

St. Petersburg, which went live immediately after Constantinople, essentially undoes one of Constantinople's upgrades, which was found to be a security risk.

Major upgrades (also called hard forks) of blockchain-based systems such as Ethereum can be tricky as they require participants on the network to switch to new software. If they don't, the fork becomes contentious -- the blockchain splits in two with some users switching to the new version and some staying on the old one.

Constantinople and St. Petersburg were activated at block height 7,280,000 or roughly at 8pm UTC on Thursday. More than 3,700 blocks were mined on Ethereum since then, and everything points to the fork going as planned.

The price of Ethereum is slightly down in the last 24 hours according to CoinMarketCap, having fallen roughly 1% to $136.81.

Disclosure: The author of this text owns, or has recently owned, a number of cryptocurrencies, including BTC and ETH.