Lint and Cleanup
XML Lint Error Guide
Decode common XML lint errors, line-column messages, malformed tags, escaping mistakes and namespace problems before fixing production payloads. This reference is written for developers who need practical validation behavior, reviewable rules and safe examples rather than copied snippets with no explanation.
Recommended workflow
| Step | Why it matters |
|---|---|
| Read the first error first | Later XML errors are often side effects of one missing bracket, quote or closing tag. |
| Check escaping | Raw ampersands and angle brackets inside text nodes are common payload failures. |
| Verify namespaces | A valid-looking tag can fail when the namespace declaration is missing or mismatched. |
| Retest after each fix | One small XML repair can change the next reported line number. |
Starter snippet
xmllint --noout payload.xml
# Check the first reported line, then validate again after each fix.Review checks
- Confirm every opening tag has the intended closing tag.
- Escape text values before pasting examples into public tools.
- Keep sample XML small enough to inspect manually.
- Separate well-formedness errors from schema validation errors.
Common mistakes
- Starting with schema rules before the document is well formed.
- Sharing private XML payloads without redaction.
- Fixing all reported lines at once and losing the original root cause.
Validation should help users correct input while protecting systems from bad data. Keep syntax checks, product policy, security review and deliverability checks separate.
Related Formalint references
Continue with Xml Linter, Xml Namespace Debugging Guide, Xml Schema Xsd Guide.