XML Validator
Validate XML well-formedness online. Shows parse errors, element count, depth, and attribute stats. Uses native browser DOMParser. 100% client-side.
Paste XML and instantly see whether it is well-formed. The validator uses the browser's native
DOMParser
API and reports parse errors with context. On valid XML, it displays a summary of the document
structure: element count, attribute count, text nodes, and maximum nesting depth.
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Frequently asked questions
What does "well-formed" mean for XML?
A well-formed XML document follows the basic syntax rules of XML: every opening tag has
a matching closing tag, elements are properly nested (no overlapping), attribute values
are quoted, and special characters like <
and & are properly escaped.
Well-formedness is a prerequisite — a parser will refuse to process malformed XML.
What is the difference between well-formed and valid XML?
A well-formed document follows XML syntax rules. A valid document additionally conforms to a schema (DTD, XSD, or RELAX NG) that defines what elements and attributes are permitted. This tool only checks well-formedness. Schema validation requires the schema document itself and tools like Saxon, Xerces, or xmllint.
Common XML errors and how to fix them
Unclosed tag: Every element needs a closing tag or be self-closing: <br/>.
Unescaped characters: Use
&,
<,
> in content.
Unquoted attributes: Always quote attribute values.
Does this tool support XML namespaces?
Yes. The browser's DOMParser
fully supports XML namespaces (the xmlns
attribute and namespace-prefixed elements). Namespace declarations are preserved and
namespace-prefixed elements are correctly parsed.
Can I validate XHTML with this tool?
Yes, if your XHTML is served as XML (application/xhtml+xml).
XHTML is a strict XML-based version of HTML, so well-formedness rules apply. However,
this tool won't validate against the XHTML DTD — it only checks XML syntax.