XML error reference · XV009
Duplicate attribute
The same attribute name appears twice on one element.
What your parser calls it
The same problem, reported differently by each parser. If you arrived here from one of these strings, you are in the right place.
| Parser | Message |
|---|---|
| libxml2 / xmllint | Attribute role redefined |
| Firefox DOMParser | XML Parsing Error: duplicate attribute |
| .NET XmlException | 'role' is a duplicate attribute name. |
What causes it
An element may not carry the same attribute twice. That is the specification's Unique Att Spec constraint. Because the check is on the expanded name, two different prefixes bound to the same namespace URI also collide even though the text differs. Merging attribute maps in code, or templating that emits a default and then an override, are the usual causes.
See it happen
<user id="1" role="admin" role="editor"/><user id="1" role="editor"/>How to fix it
Remove the duplicate and keep the value you actually want. When attributes are built programmatically, use a map keyed by expanded name so a later write replaces the earlier one instead of appending a second attribute.
Fix your own document
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