FIX versions
This reference and the decoder cover three dictionary versions. All are shipped as npm packages and all run in the browser.
FIX 4.4912 fields · 93 messages · 105 componentsFIX 4.2405 fields · 46 messages · 2 componentsFIX 5.0 SP21452 fields · 115 messages · 176 components
Which one am I looking at?
Read BeginString, tag 8 — it is the first field of every message. FIX.4.4 and FIX.4.2 name the version directly. FIXT.1.1 means the message rides the FIXT transport (FIX 5.0 onwards); the application version then travels in ApplVerID (1128) or the session's DefaultApplVerID (1137). The decoder handles all of this automatically. See FIX 4.4 vs FIX 4.2 for what actually differs in 4.x.