w:tag (Structured Document Tag Programmatic Tag)

Provides a programmatic identifier for a structured document tag, used by code to locate or process the SDT independently of its display name.

Parent elements

w:sdtPr

Description

w:tag stores a programmatic string identifier for an SDT. Unlike w:alias (which is a user-visible display name), w:tag is intended for use by code — for example, to find all content controls with a specific tag and populate them with data.

It is defined in ECMA-376 Part 1 §17.5.2.40.

Tag values are arbitrary strings and need not be unique in a document, though uniqueness is often desirable in practice.

Attributes

Attribute	Type	Possible Values	Description
`w:val`	`xsd:string`	Any string	Programmatic identifier for the SDT.

Examples

<w:sdtPr>
  <w:alias w:val="Invoice Date"/>
  <w:tag w:val="invoiceDate"/>
  <w:date/>
</w:sdtPr>

using DocumentFormat.OpenXml.Wordprocessing;
using System.Linq;

// Set a tag on an SDT
var sdtPr = new SdtProperties(
    new SdtAlias { Val = "Invoice Date" },
    new Tag { Val = "invoiceDate" },
    new SdtDate()
);

// Find all SDTs with a specific tag
var controls = document.Body
    .Descendants<SdtElement>()
    .Where(sdt => sdt.SdtProperties?
        .Descendants<Tag>()
        .FirstOrDefault()?.Val == "invoiceDate");

Notes

w:tag corresponds to the “Tag” field in the Content Control Properties dialog in Word.
When using data binding via w:dataBinding, the tag is often used in conjunction with XPath expressions for disambiguation.