The <thead> Element

Technical Summary

Definition, placement, and content model

Core definition of the thead element

Property	Specification	Conditions and scope
Meaning	Row group of column labels and ancillary cells	Distinct from the header or data semantics of each cell
Context	Child of table	After caption and colgroup; before the table body, tfoot, and direct tr children; at most one direct child
Content model	Zero or more tr and script-supporting elements	Each row may contain td or th cells
Start and end tags	Start tag is required	End tag may be omitted only when immediately followed by tbody or tfoot
DOM interface	HTMLTableSectionElement	Shared with tbody and tfoot
Specific attributes	None	Global attributes apply

HTML conformance and parser recovery are separate questions. A parser constructing a DOM from malformed input does not make that input conforming HTML.

thead, th, and the table model

Elements with distinct meanings inside a table

Element	Structural role	Cell semantics
thead	Row group in the heading section	The section alone does not make each cell a header cell
th	Cell in a row	Header cell; scope and the header-assignment algorithm determine its associations
tbody	Row group in the table body	A th inside it can serve as a row header
td	Cell in a row	Data cell

The HTML Standard's definition of thead allows ancillary non-header cells in addition to column-label rows. Do not infer header relationships from section membership alone; inspect the cell elements and table model.

Complex tables may involve th attributes scope, id, and headers, row and column groups, and cell spans. The section name thead alone does not determine every cell association or announcement order.

DOM constructed by the parser

<table id="schedule">
  <tr><th scope="col">Day</th></tr>
</table>

// DOM constructed by the HTML parser
table#schedule
└─ tbody  (inserted implicitly)
   └─ tr
      └─ th

In the table insertion mode, when a tr token occurs outside a permitted table section, the tree builder inserts an implied tbody and reprocesses the token. It does not infer thead from a th cell. For conforming authoring markup, make thead the explicit parent of heading rows.

HTMLTableSectionElement and table APIs

Main APIs used with thead

Member	Result or behavior	Scope and boundary
table.tHead	Returns the first direct thead child	Returns null when there is none
table.createTHead()	Returns the first existing thead or a newly created section	A new section is inserted after caption and colgroup
table.deleteTHead()	Removes the first direct thead child	Does nothing when there is none
thead.rows	An HTMLCollection of direct tr children	Live collection; reflects row insertions and removals
thead.insertRow() / deleteRow()	Insert or remove rows in the section	Indexes are relative to rows in this section

const table = document.querySelector("table");
const head = table.tHead;              // Existing thead, or null
const sameHead = table.createTHead();  // Returns the existing section if present
head.rows.length;                      // Number of tr elements in thead

table.rows is the row collection for the whole table; thead.rows is the collection for the header section. Their names are similar, but their scopes differ. createTHead() creates a section; it does not create th cells or row content.

Accessibility mapping

HTML-AAM maps native thead to the WAI-ARIA rowgroup role. This exposes the header row-group structure; it does not assign header-cell roles to the cells in that group. Header cells are distinguished using th and table rules involving attributes such as scope.

The AAM measurement on this page uses Chrome browser role and name queries. It is not itself the normative HTML-AAM mapping, a record from a platform API such as Windows UI Automation, or an assistive-technology speech observation.

Facts and evidence

Normative specification claims, AAM mappings, and implementation results from selected environments are recorded separately.

Evidence

1. HTML Standard: The thead element — context, content model, tag omission, and section interface
2. HTML Standard: The table element — table child structure and APIs
3. HTML Standard: The “in table” insertion mode — implied tbody insertion and token reprocessing
4. HTML Accessibility API Mappings: thead — rowgroup mapping
5. Web Platform Tests: the-thead-element/rows.html — section row collection
6. Web Platform Tests: the-table-element/tHead.html — table.tHead behavior

Implementation evidence

Specification requirements, browser observations in selected environments, WPT runs, and accessibility role/name queries are recorded separately. Each result is limited to its stated fixture, browser, and test scope.

Coverage and open issues

• SPECElement meaning, placement, content model, tag omission, DOM interface, table parsing, table APIs, and HTML-AAM role mapping reviewed
• IMPLLimited to the fixture and one Chrome environment. Other browsers, OS builds, and print behavior are unmeasured
• WPTSelected tests only. The upstream revision served by wpt.live is not pinned; other browsers and the full directory are unchecked
• AAMBrowser role/name queries measured. Platform accessibility APIs, assistive-technology speech, and cross-environment comparisons are untested
• ReviewExpert-gap Review has not been completed

This Topic has initial coverage. Passing the selected fixture and tests does not establish the same result for every HTML structure, browser, operating system, or assistive technology.

Related surfaces

Column-group rules and measurements are covered in the colgroup Topic; a beginner-friendly example is in How to Use the colgroup Element.

For a beginner-friendly example, see How to Use the thead Element in Yugien. The whole table model is covered in the table Topic; header cells and cell associations in the th Topic; body row groups in the tbody Topic; summary row groups in the tfoot Topic; and row structure in the tr Topic.