Shanghai Upgrade is a hard fork of the Bitcoin Cash (BCH) blockchain that took place on November 15th, 2020. The upgrade was proposed by ViaBTC and its primary purpose was to increase the block size limit from 8 megabytes to 32 megabytes in order to improve scalability and transaction throughput capacity. Additionally, it also included changes such as adding new opcodes for advanced scripting capabilities and increasing the default data-carrier-size limit from 80 bytes to 220 bytes.
The majority of miners, exchanges, wallet providers and other stakeholders who participated in the process agreed with these changes and supported them accordingly. As a result of this support, there were two distinct versions of BCH created: BCHN (Bitcoin Cash Node) which adopted all updates proposed by Shanghai Upgrade; and BCKABC (Bitcoin Cash ABC), which kept most features unchanged but implemented additional replay protection measures specified by Amaury Séchet’s team at Bitcoin ABC.
It should be noted that while both nodes are still running on the same chain they now have incompatible consensus rules due to their respective implementations of China’s upgrade proposals; meaning transactions on one node may not be valid on another node without specific modifications made beforehand. This has caused some controversy within the community since users must choose between one version or another for their transactions depending upon where they want them validated/confirmed firstly; thus potentially leading to confusion among less experienced users who might not know about these changes or how they affect them directly.
