NoUsernames (FIX tag 809)

NumInGroupFIX 5.0 SP2group counter

NoUsernames (tag 809) is a NumInGroup field defined in FIX 5.0 SP2. It appears in 1 message type, always optionally. Its datatype is NumInGroup, which makes it a repeating-group counter: its value is the number of entries that follow, not a quantity in its own right.

At a glance

Tag: 809
Name: NoUsernames
Datatype: NumInGroup (int)
Dialects: FIX 5.0 SP2
Messages: 1

What the specification says

Number of Usernames to which this this response is directed

Descriptions are quoted from the FIX Orchestra sources under the Apache 2.0 licence.

A real message using tag 809

UserNotification · FIX 5.0 SP2

Tag	Field	Wire value	Meaning
8	BeginString	FIXT.1.1
9	BodyLength	100
35	MsgType	CB	UserNotification
49	SenderCompID	BOARTEAM
56	TargetCompID	COUNTERPARTY
34	MsgSeqNum	2
52	SendingTime	20240101-12:00:00.000
809	NoUsernames2 entries	2	repeating group
553	Username	EXAMPLE
553	Username	EXAMPLE
926	UserStatus	1	Logged In
10	CheckSum	104

Edit and decode it yourself

Shown with | separators for readability. On the wire FIX uses SOH (0x01), an invisible control byte — and because BodyLength and CheckSum are computed over the actual bytes, the two forms have different checksums. Both are valid and both decode here.

Open in the full decoder →

Generated from the FIX 5.0 SP2 dictionary and verified at build time: it parses and validates with no issues. Open the decoder to try your own message.

Where tag 809 appears

Requiredness is a property of the message, not of the field: the same tag can be optional in one message and conditionally required in another.

Message	MsgType	Requiredness	Where in the message
UserNotification	CB	Optional	inside the UsernameGrp component

Wire format

The number of entries in the repeating group that follows. The next field on the wire is the group's delimiter tag. @boarteam/fix parses the value as a number and reports parse/invalid-int when it does not lex as one; the raw string is kept either way.

Read tag 809 in TypeScript

decode.tsts

import { createFixEngine } from "@boarteam/fix";import { dictionary } from "@boarteam/fix-dict-fix50sp2";const fix = createFixEngine(dictionary);const { message, issues } = fix.parse(raw);// NoUsernames is a group counter, so the entries live on message.groups —// NOT on message.fields. message.fields[809] is undefined.const entries = message.groups[809] ?? [];for (const entry of entries) {  // entry.fields is keyed by tag; entry.groups holds nested groups}

Decode this in your own code

The same engine that produced the decoded example above is an Apache-2.0 npm package with zero runtime dependencies. It runs in Node and in the browser, and parse() returns problems as data instead of throwing.

npm i @boarteam/fix @boarteam/fix-dict-fix50sp2

Try the decoder Source on GitHub