DataFormattools
XML · Validator

XML Validator & Well-Formed Checker

Validate XML syntax and well-formedness online. Detect unclosed tags, attribute syntax mistakes, and XML parsing errors with exact line numbers.

Syntax & Structure Validator
Paste or type data below to validate syntax and structure in real time.
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100% In-Browser Privacy: All conversions, formatting, and validations run purely on your machine using client-side JavaScript. Your data, code snippets, and environment variables are never transmitted to any server or recorded in logs.
Specifications

How XML Validator Works

  • Parses XML using the browser native DOMParser XML engine.
  • Checks for well-formedness rules (single root, matching tag pairs, valid entity references).
  • Reports syntax errors with exact line numbers.
Demonstration

Example Input & Output

Verifies that the XML document has a single root element, matching start/end tags, and valid attribute quoting.

XML Source
<?xml version="1.0" encoding="UTF-8"?>
<note>
  <to>Tove</to>
  <from>Jani</from>
  <heading>Reminder</heading>
  <body>Don't forget the meeting!</body>
</note>
Expected Output
✓ Valid XML (Well-Formed Document)
Applications

Common Use Cases

Pre-deployment Config Validation

Verify web.config, pom.xml, and AndroidManifest.xml before compilation.

RSS / Atom Feed Checks

Validate XML feed structures before publishing.

Guidelines

Key Specifications & Gotchas

Multiple Root Elements

XML documents must have exactly one root element.

Case Mismatch in Tags

XML is strictly case-sensitive; <Tag> and </tag> do not match.

Questions

Frequently Asked Questions

What is a well-formed XML document?

A well-formed XML document has matching opening/closing tags, proper nesting, attribute quotes, and a single root element.

How do I find XML syntax errors?

Paste your XML; the validator highlights the exact line and character where parsing failed.

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