HL7 v2 versions (2.3 through 2.8)

HL7 v2 is a family of versions, not one standard: 2.3, 2.3.1, 2.4, 2.5, 2.5.1, 2.6, 2.7, and 2.8 are the versions in production use. Each message declares its version in MSH-12, and later versions add fields and segments, retype datatypes (PID-7 moves from TS to DTM at 2.6, PID-8 from IS to CWE at 2.7), and withdraw fields, while keeping the wire format backward-recognizable. In practice most US hospital traffic still runs 2.3 through 2.5.1, so version skew between interface partners is routine and interfaces are negotiated per version.

Example

v2.3:
MSH|^~\&|PIDGEON^^L|PIDGEON_FACILITY|TARGET^^L|TARGET_FACILITY|20260722160847||ADT^A01^ADT_A01|984078|P|2.3||||||8859/8|zh^Chinese^ISO639^^^

v2.7, same generator, same seed:
MSH|^~\&|PIDGEON^^L|PIDGEON_FACILITY|TARGET^^L|TARGET_FACILITY|20260722160854||ADT^A01^ADT_A01|984078|P|2.7|||||USA|8859/15|zh^Chinese^ISO639^^^^^^^^^^^^^^^^^^^|ISO 2022-1994|ID239056^^^||||^ID164038^Random

Engine-generated with `pidgeon generate ADT^A01 --seed 42` and `--hl7-version 2.7` (timestamps vary per run; the control ID 984078 is identical because the seed drives it). The 2.7 MSH carries fields 2.3 does not define (country code, alternate character set handling scheme, sending/receiving network address), and its CWE coded values carry more components.

Validation context

Strict and compatibility validation notes land here with the phase-1 data export.