Version 3.0.0 This change log summarizes all the changes since the last stable release (v2.6.1). See the last section about changes since v3.0.0-beta-4. Proto3 Introduced Protocol Buffers language version 3 (aka proto3). When protocol buffers was initially open sourced it implemented Protocol Buffers language version 2 (aka proto2), which is why the version number started from v2.0.0. From v3.0.0,