XML Validator

Check XML well-formedness instantly and get clear feedback on exactly what is wrong and where

Input

Validation Results

Enter or paste your XML to validate

What is XML Validator?

Ever shipped an XML config or a SOAP request only to have the other side reject it with a cryptic "parse error"? Tracking down a single unclosed tag in a wall of markup is no fun. XML Validator checks your document for well-formedness the instant you paste it and tells you, in plain language, whether the XML is good to go—and if not, where the trouble starts.

Well-formed XML follows a small set of strict rules: every element has a matching closing tag, attributes are quoted, there is exactly one root element, and reserved characters are escaped. We built this validator on the browser's native DOMParser, the same engine real applications use, so what passes here passes in production. For the formal rules, the W3C XML 1.0 specification is the source of truth, and MDN's XML introduction explains the concepts in friendlier terms.

How to Use XML Validator

  1. Paste or Upload Your XML – Copy your XML into the input panel, or click "Upload" to load an .xml file from your computer.
  2. Automatic Validation – The tool checks your XML the moment you type or paste. There is no button to press—results update in real time.
  3. Review the Result – The right panel shows a green "Valid XML!" message with statistics, or a red message that points to the line and column where parsing broke.
  4. Fix and Re-check – Read the error message, fix the offending tag or attribute in the input, and watch the panel turn green.
  5. Format Once Valid – When your XML is well-formed, hit "Format" to pretty-print it with clean indentation.

Pro Tip: Use the "Invalid Sample" button to see what a well-formedness error looks like, or "Sample" to load a clean XML example you can edit.

Example

A common mistake — an unclosed tag — caught by the validator. The right panel shows the kind of feedback you would see.

Invalid XML → Validation error Validate
subscriber.xmlInvalid · 1 error
<subscriber>
  <subscriberId>SUB-1001</subscriberId>
  <msisdn>447700900142</msisdn>
  <plan>Unlimited 5G<plan>
  <roaming>true</roaming>
</subscriber>
Validation result1 issue found
✗ Invalid XML

Line 4
Error: Opening and ending tag
mismatch: plan line 4 and plan.

The <plan> element is opened twice
instead of being closed with
</plan>, so the parser cannot
match the tags.

Common Use Cases

Validating SOAP Requests and Responses

Many telecom and enterprise back ends still exchange SOAP, and a malformed envelope gets rejected at the door. Paste the request here before you send it and confirm it is well-formed first—that rules out the easy class of failures before you start blaming the service. For the envelope rules, the W3C SOAP specification spells out the structure.

Checking Configuration and Feed Files

Build manifests, app-server configs, RSS feeds, and SIM provisioning files are all XML, and one bad character can take a whole service down on startup. Validate the file here before you commit or deploy. If you also need to confirm a file against a public service, the W3C validator is a useful second opinion.

Learning XML Syntax

If you are getting comfortable with XML, the validator is a fast feedback loop: change a tag, see immediately whether it is still well-formed, and learn the rules by doing. For a structured walkthrough, W3Schools' XML tutorial covers the basics step by step.

Key Features

  • Real-Time Validation – Checks XML well-formedness as you type, with instant feedback and no button to press.
  • Clear Error Reporting – Surfaces the parser's message so you know what broke and roughly where.
  • XML Statistics – For valid XML, shows size, line count, total element count, and nesting depth.
  • Native Parser – Uses the browser's DOMParser, the same engine real applications rely on.
  • File Upload Support – Load .xml files directly instead of copy-pasting, handy for larger documents.
  • Format When Valid – Pretty-print well-formed XML with one click.
  • Sample Data – Load valid or deliberately broken XML to see how the validator behaves.

Frequently Asked Questions

Is my XML data safe when I use this validator?

Yes. All validation runs entirely in your browser using the native DOMParser. Your XML is never uploaded to a server or stored anywhere—it stays on your device, so your data remains private.

What's the difference between well-formed and valid XML?

Well-formed means the document follows XML's structural rules: closed tags, quoted attributes, a single root. Valid (in the strict sense) means it also conforms to a schema like a DTD or XSD. This tool checks well-formedness, which is the first thing every XML parser requires. For schema-level checks, the W3C XML Schema specification is the reference.

What kinds of errors does it catch?

It catches every well-formedness problem: unclosed or mismatched tags, unquoted attributes, multiple root elements, illegal characters, and stray ampersands that should be written as &. If any of those are present, you get an error instead of a green check.

Can I validate large XML files?

Yes. The validator handles large documents efficiently because it runs on the browser's optimized parser. Very large files may take a moment, but everything stays local with no server-side limits.

Does it work on mobile devices?

Yes. The tool is fully responsive and works on phones and tablets, with the panels stacking vertically on small screens. If you get stuck on a tricky error, Stack Overflow's XML tag covers thousands of common cases.

Related Tools

  • XML Formatter – Pretty-print and indent your XML once it is well-formed.
  • XML Minifier – Strip whitespace to shrink your XML for transport.

Useful Resources