A coordinated change to network rules that nodes adopt to gain new features or fixes.
Protocol upgrades can be soft (backward-compatible) or hard (incompatible). Nodes must update to the new rules to remain in consensus with the majority.
"Re-enabling opcodes on Bitcoin Cash required a protocol upgrade adopted by node implementations and miners."
The process often involves proposals, client implementations, testnets, and coordination among wallets, exchanges, and miners.
"Ahead of an upgrade, exchanges announce maintenance windows to ensure smooth deposits and withdrawals."
All terms and definitions may update as the Cryptionary improves.