The upgrade means that the two networks share virtually the same protocol, making them fully intercompatible.
The hard fork was scheduled for block 10,500,839, which was mined at 8:00 p.m. Eastern time on May 31.
The fork is the third in a series of recent upgrades. In December, the Agharta fork ported Constantinople features to ETC, while Atlantis was activated earlier in September 2019.
Ethereum developer Afri Schoedon says that the inclusion of Istanbul features means that the two projects “reached protocol parity.”
However, some minor inconveniences occurred as a result of the fork, with a small portion of miners remaining on the old chain.
Some clients have also not been synchronized with the hard fork, notably- Hyperledger Besu. The ETC team said that this should not affect the network as Besu was primarily used in enterprise settings.