XML Tools
XML Validator Online Free
Validate XML syntax online and find malformed tags, attributes, entities and document structure errors.
XML validation guide
Find malformed XML before integration
An XML syntax validator checks well-formedness: one root element, balanced tags, quoted attributes and valid character usage. A well-formed document can still fail XSD, namespace or application requirements, so use schema validation and target-system testing when a formal contract exists.
Step-by-step
A reliable workflow
Paste the complete XML document.
Run validation and inspect the first error.
Correct the surrounding tag, attribute or entity.
Validate again, then check any required XSD or application rules.
Practical use cases
SOAP and XML APIs
Catch malformed request or response bodies.
Configuration
Check XML settings before application startup.
Data feeds
Detect broken RSS, Atom or partner feeds.
File exchange
Verify well-formedness before importing documents.
Common mistakes
- ⚠Confusing well-formed XML with XSD-valid XML
- ⚠Ignoring namespace errors
- ⚠Fixing a later parser error before the first one
- ⚠Using unescaped ampersands or reserved characters
Professional tips
- ✓Start with the first error
- ✓Format the XML to expose hierarchy
- ✓Check encoding declarations
- ✓Validate against XSD where available
Continue the workflow
Frequently asked questions
What makes XML well formed?+
It requires one root element, properly nested tags, quoted attributes and valid escaping.
Is well-formed XML automatically XSD valid?+
No. XSD adds rules for elements, attributes, order and data types.
Why must ampersands be escaped?+
A raw ampersand begins an entity reference and must normally be written as & in text.
Can XML have more than one root element?+
No. A document must have exactly one root element.
Why can the error location be later than the mistake?+
An unclosed quote or tag can cause the parser to fail only when it reaches later content.
How should namespaces be validated?+
Check declarations, prefixes and any schema rules required by the receiving system.
Is my input uploaded to a server?+
These FormatForge tools process supported input in your browser. Still, remove passwords, tokens, personal data and confidential production values before using any online utility.
Can I use the tool on mobile?+
Yes. Large documents, deep nesting and side-by-side comparisons are usually easier on a desktop browser with more memory and screen space.
Should I use the result directly in production?+
Review the output, validate it with the target system and test it in a safe environment before using it in production code, APIs or deployments.
Why do very large files take longer?+
Parsing, rendering, comparing and reformatting structured documents use your device processor and memory. Reduce the sample size when possible.