Help:Cite errors/Cite error references duplicate key

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Overview

A footnote used multiple times may be defined with a name:

<ref name="foo">content</ref>

To invoke a named footnote:

<ref name="foo" />

The content of the ref name "foo" is only defined once.

Issues and resolution

The error happens when a named reference is defined multiple times with different content. For example, first <ref name="foo">content1</ref> and later <ref name="foo">content2</ref>, where "foo" is repeated but content1 and content2 are different. The purpose of named references is to be able to invoke them elsewhere with <ref name="foo" />, but there must be a unique definition of the ref name "foo".

If the references with content1 and content2 are meant to be different then change one of the ref names, for example name="bar" instead of name="foo". If the reference is not meant to be invoked elsewhere then it can also be made unnamed by removing name="foo", but this is not necessary.

If the references are meant to be the same then replace one of the definitions by <ref name="foo" /> to invoke the other definition. It may technically work to make two identical definitions but this should not be done. It causes confusion and will recreate the error if somebody later changes one of the definitions without making the same change to the other.

The error can also happen with empty ref names like <ref name="">content</ref> or <ref name>content</ref>. Ref names should not be empty. Either add a name or remove name="".

Ref names may be generated by a template and produce names not in the wikitext. For example, {{sfn|Stokes|1979|p=2}} and {{sfn|Stokes|1979|pp=2}} may both produce references of form <ref name="FOOTNOTEStokes19792">...</ref>, causing the error message to use the ref name "FOOTNOTEStokes19792".

Technical

Pages with this error message are placed into Pages with incorrect ref formatting. The system message page is at Cite error references duplicate key.