How to use the XML Validator Online
1. Paste your XML document into the editor on the left.
2. Validation runs automatically — a green badge indicates well-formed XML.
3. If invalid, the first parse error is shown to help you locate the issue.
What is it?
XML validation checks that a document is "well-formed" — meaning it follows the structural rules of XML: all tags are properly closed, nested correctly, attribute values are quoted, and special characters are escaped. A well-formed XML document can be safely parsed by any XML parser.
This is an essential step before using XML in production — a malformed API request or config file can crash services or expose unexpected behaviour. The validator uses the browser's native DOMParser, giving you the same parsing result as most production XML libraries.
Example
<users>
<user>
<name>Alice</name
</user>
</users>✗ Invalid XML Parse error at line 3: expected '>' to close tag Fix: Add the missing '>' after </name
Common XML errors: unclosed tags, mismatched names, unescaped & < > characters, missing quotes on attributes.
Benefits
Find the exact line causing parse failures
Detailed error messages show line and column numbers for malformed XML — no trial-and-error scanning through the document.
Validate SOAP envelopes and XML API responses
Ensure XML-based APIs and SOAP services return well-formed documents before your parser encounters an exception.
Confirm RSS and Atom feed validity
Well-formed feeds index correctly in feed readers and aggregators — a malformed tag breaks the entire feed for subscribers.
Catch unclosed tags and missing namespaces
The most common XML errors — unclosed elements, missing namespace declarations — are flagged with the exact location.
Frequently asked questions
What is the difference between well-formed and valid XML?
Well-formed XML follows structural syntax rules (correct tags, nesting, encoding). Valid XML additionally conforms to a specific schema (XSD or DTD) that defines which elements and attributes are allowed. This tool checks well-formedness.
What are the most common XML errors?
The most common errors are: unclosed tags (<item> without </item>), mismatched tag names (<Item> vs </item>), unescaped special characters (& should be &, < should be <), and missing quotes around attribute values.
Do I need the XML declaration at the top?
The <?xml version='1.0' encoding='UTF-8'?> declaration is technically optional for UTF-8 documents but strongly recommended. It tells parsers the version and character encoding, preventing issues with special characters.