CJK Unified Ideographs Extension I is a Unicode block comprising CJK Unified Ideographs included in drafts of an amendment to China's GB 18030 standard circulated in 2022 and 2023, which were fast-tracked into Unicode in 2023.
It defines a Unicode Transformation Format which retains compatibility with existing data in the earlier GBK and EUC-CN character encodings, and specifies particular Unicode characters which devices sold in China must support.
The Chinese national body maintained that "ISO/IEC 10646 do not specify the purpose of the 0A plane", which ISO 10646 denotes as "reserved for future standardization", and that this use was therefore "not inappropriate".
[5] However, since the intent of ISO 10646 was for Plane 10 to be reserved for future allocation by ISO 10646 and Unicode via their usual ballot process, not for it to be allocated unilaterally by national standards bodies, this proposed move was criticised by experts and other national bodies as one which would "destabilize the synchronization" between GB 18030 and ISO/IEC 10646 (and thus Unicode), and which would make it impossible to conform to both with a single implementation,[5] effectively forking Unicode.
[7] As an alternative, the repertoire (eventually reduced to 622 characters after expert review) was fast-tracked into Unicode version 15.1 in September 2023, as the CJK Unified Ideographs Extension I block.