generated: '2026-09-01'
method: searched
source: https://apidocs.tzero.com/docs/fix
note: >-
  tZERO publishes no product changelog or release-notes feed for its REST APIs. The only dated,
  versioned change record on the developer surface is the Revision History table carried inside
  each FIX specification page. Those are captured verbatim below. The Institutional OpenAPI
  carries info.version 1.1.0 with no dated history; the Issuance & Secondary Markets OpenAPI
  declares no version at all.
scheme: per-document revision history (FIX specs) + semver in OpenAPI info.version (Institutional)
current_version:
  institutional_openapi: 1.1.0
  issuance_secondary_markets_openapi: null
  fix_market_data_spec: '8 (2025-12-20)'
  fix_ioi_market_data_spec: '1.2 (2025-12-20)'
documents:
- document: FIX 4.4 Market Data Specification
  url: https://apidocs.tzero.com/docs/fix/market-data
  footer: tZERO Technologies · FIX 4.4 Market Data Specification · December 2025
  entries:
  - {version: '8', date: '2025-12-20', highlights: ['Added updated tZERO logo to the heading'], breaking: false}
  - {version: '7', date: '2020-10-27', highlights: ['Added tag 8724 ShortSellRstrcn to the Security Status message', 'Removed "not supported" text for tag 266 AggregatedBook=N', 'Grammar updates'], breaking: false}
  - {version: '6', date: '2020-08-19', highlights: ['Added table of contents', 'Added additional values to tag 269 MDEntryType', 'Added additional values to tag 327 HaltReason', 'Added Revision History section'], breaking: false}
  - {version: '5', date: '2020-01-06', highlights: ['Added Auction State (90) to tag 327 HaltReason'], breaking: false}
  - {version: '4', date: '2019-11-05', highlights: ['Redefined tag 277 TradeCondition to account for imbalances'], breaking: true}
  - {version: '3', date: '2019-09-17', highlights: ['Added tZERO logo to the heading'], breaking: false}
  - {version: '2', date: '2019-08-12', highlights: ['Added disconnect behavior to Scenarios section', 'Added Trading Session Status Request message', 'Added Security Status Request message'], breaking: false}
  - {version: '1', date: '2019-07-12', highlights: ['Added values for tag 277 TradeCondition', 'Added tag 893 LastFragment to Market Data Snapshot', 'Split scenario diagrams into their own section'], breaking: false}
  - {version: '0', date: '2019-07-03', highlights: ['Original'], breaking: false}
- document: FIX IOI Market Data Specification
  url: https://apidocs.tzero.com/docs/fix/ioi-market-data
  entries:
  - {version: '1.2', date: '2025-12-20', highlights: ['Incorporated new tZERO logo'], breaking: false}
  - {version: '1', date: '2022-07-28', highlights: ['Added milliseconds to timestamps', 'Added MDEntryDate and MDEntryTime to Market Data Snapshot', 'Added Market Data Request message type'], breaking: false}
  - {version: '0', date: '2017-07-18', highlights: ['Original'], breaking: false}
- document: FIX 4.4 DROPCOPY Specification
  url: https://apidocs.tzero.com/docs/fix/drop-copy
  footer: tZERO Technologies · FIX 4.4 DROPCOPY Specification · December 2025
  entries: []
  note: page carries a Revision History heading in the nav but no populated table
- document: FIX 4.2 Order Entry Specification
  url: https://apidocs.tzero.com/docs/fix/order-entry
  entries: []
  note: page carries a Revision History heading in the nav but no populated table