EncodedSubjectLen (FIX tag 356)

LengthFIX 4.4FIX 4.2

EncodedSubjectLen (tag 356) is a Length field defined in FIX 4.4 and FIX 4.2. It appears in 1 message type, always optionally.

At a glance

Tag: 356
Name: EncodedSubjectLen
Datatype: Length (int)
Dialects: FIX 4.4 and FIX 4.2
Messages: 1

What the specification says

FIX 4.4

Byte length of encoded (non-ASCII characters) EncodedSubject (357) field.

FIX 4.2

Byte length of encoded (non-ASCII characters) EncodedSubject field.

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

A real message using tag 356

Email · FIX 4.4

Tag	Field	Wire value	Meaning
8	BeginString	FIX.4.4
9	BodyLength	157
35	MsgType	C	Email
49	SenderCompID	BOARTEAM
56	TargetCompID	COUNTERPARTY
34	MsgSeqNum	2
52	SendingTime	20240101-12:00:00.000
164	EmailThreadID	EXAMPLE
94	EmailType	0	New
147	Subject	EXAMPLE
356	EncodedSubjectLen	7
33	NoLinesOfText1 entry	1	repeating group
58	Text	Example message generated from the FIX dictionary.
10	CheckSum	142

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 4.4 dictionary and verified at build time: it parses and validates with no issues. Open the decoder to try your own message.

Where tag 356 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	FIX 4.4	FIX 4.2	Where in the message
Email	C	Conditional	Optional	directly on the message body

Wire format

A byte count for the length-prefixed field that follows it. Count bytes, not characters — a multi-byte UTF-8 value makes the two differ. @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 356 in TypeScript

decode.tsts

import { createFixEngine } from "@boarteam/fix";import { dictionary } from "@boarteam/fix-dict-fix44";const fix = createFixEngine(dictionary);const { message, issues } = fix.parse(raw);const field = message.fields[356];field?.name;   // "EncodedSubjectLen"field?.raw;    // the verbatim wire stringfield?.value;  // coerced to a number

Other Length fields

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-fix44

Try the decoder Source on GitHub