sfmc.guide
Engagement Next
⌘K

Length

Measures the size of a string. Runtime-proven on a live Marketing Cloud Engagement CloudPage — including the counting unit, which is UTF-16 code units rather than user-visible characters.

Next
Runtime verified Test scripts included

Syntax

Length(sourceString)  →  number
1 argument — exactly

Parameters

Name Type Required Description
sourceString string | number | date Yes Value to measure

Example

%%[
  VAR @size
  SET @size = Length("Hello")
]%%
Length: %%=v(@size)=%%

Renders Length: 5.

The usual use is guarding an optional field before rendering it:

%%[
  IF Length(AttributeValue("FirstName")) > 0 THEN
]%%
  Hi %%=v(AttributeValue("FirstName"))=%%,
%%[ ELSE ]%%
  Hi there,
%%[ ENDIF ]%%

The count is in UTF-16 code units, so an emoji counts as two — see below before using it as a character limit.

Return value

number — the count of UTF-16 code units in the value.

Every successful call rendered a bare non-negative integer. There is no closed set of sentinel values.

Behaviour

Plain ASCII counts one per character. Length("Hello") gives 5 and Length("Hello World") gives 11.

An empty string measures 0.

Numbers are measured by their string form. Length(12345) gives 5.

Date values are measured by their formatted string. Length(Now()) gave 19, matching the length of the rendered date.

Booleans are swallowed silently. Length(true) returns HTTP 200 and renders 0 — the boolean contributes nothing measurable. That is a rejection rather than boolean support, so the parameter type stays string | number | date. The same swallowing happens across the String family; see Differs from official docs.

The counting unit is UTF-16 code units

This is the load-bearing finding for this function, and the official reference does not define the unit at all.

Call Renders
a four-letter ASCII word 4
a four-letter word ending in a precomposed accented e 4
a six-letter German word containing the sharp s 6
a single emoji from outside the Basic Multilingual Plane 2

The emoji is one user-visible character but two code units, and Length reports 2. This was settled by dumping the codepoints of the echoed input alongside the returned count: the emoji echoed as the surrogate pair 55357/56832, the accented letter echoed as the single codepoint 233, so a mis-decoding console could not have manufactured the result.

The practical consequence is truncation and validation. A limit enforced with Length accepts one fewer user-visible character as soon as an emoji is involved, and cutting a string at a code-unit position can split a surrogate pair. The finding is catalogued on Differs from official docs.

Show test script
%%[
  VAR @b
  SET @b = RequestParameter("b")

  /* safe sweep: plain ASCII */
  IF @b == "safe" THEN
    OutputLine(Concat("L5=[", Length("Hello"), "]"))
    OutputLine(Concat("L11=[", Length("Hello World"), "]"))
  ENDIF

  /* counting unit: echo the input next to the count so the codepoints can be dumped */
  IF @b == "nal" THEN
    OutputLine(Concat("NAL_ASCII4=[", Length("abcd"), "]"))
    OutputLine(Concat("NAL_ECHO_CAFE=[", "café", "]"))
    OutputLine(Concat("NAL_CAFE=[", Length("café"), "]"))
    OutputLine(Concat("NAL_ECHO_SS=[", "Straße", "]"))
    OutputLine(Concat("NAL_SS=[", Length("Straße"), "]"))
    OutputLine(Concat("NAL_ECHO_EMO=[", "😀", "]"))
    OutputLine(Concat("NAL_EMO=[", Length("😀"), "]"))
  ENDIF

  /* empty string */
  IF @b == "empty" THEN
    OutputLine(Concat("LE=[", Length(""), "]"))
  ENDIF

  /* numbers and dates are measured by their string form */
  IF @b == "ln" THEN
    OutputLine(Concat("LN=[", Length(12345), "]"))
  ENDIF

  IF @b == "ld" THEN
    OutputLine(Concat("LD_ECHO=[", Now(), "]"))
    OutputLine(Concat("LD=[", Length(Now()), "]"))
  ENDIF

  /* boolean: HTTP 200, renders 0 */
  IF @b == "lb" THEN
    OutputLine(Concat("LB=[", Length(true), "]"))
  ENDIF

  /* each arity branch aborts the page: the start marker never renders */
  IF @b == "l0" THEN
    OutputLine(Concat("--- l0 start ---"))
    OutputLine(Concat("L0=[", Length(), "]"))
  ENDIF

  IF @b == "l2" THEN
    OutputLine(Concat("--- l2 start ---"))
    OutputLine(Concat("L2=[", Length("a", "b"), "]"))
  ENDIF
]%%

Availability

Platform Available
Marketing Cloud Engagement Yes
Marketing Cloud Next Yes, from API 67.0

See also