{{Author missing}} (or {{author?}} for short) is an inline cleanup template flagging a broken source citation that is missing author information (or at least the specified fact that author information is not available).
For all citations, append the tag to the end of the citation (usually just before the closing reference tag </ref>):
{{author missing|date=January 2025}}
In the occasional case of a partial name (e.g. just a family name, or some construction such as "Dr. Falstaff" or "Reagan and Parkes" or "VNEA" without the full information being provided in a "Notes", "References" or "Bibliography" section elsewhere on the page), you can change the displayed text to [author incomplete] using:
or for a committee, working group, etc., instead of individual author names:
|author=Organizational author
For a free-form citation:
Just add the name(s) as appropriate to the format of the citation; or...
Better yet, convert the entire citation to {{cite journal}}, {{cite news}} or some other {{cite xxx}}-series template, as appropriate for the work in question.
If you know that no author was specified by the original source, as in common in many newswires, explicitly state this with:
|author=<!--none-->
or for free-form citations:
<!--No author specified by source.-->
Do not use question marks.
Do not just repeat the publisher, work (publication/site) name, or other field.
Do not leave the information blank and untag it, or someone else will just come along later and flag this with {{author missing}} again! The citation templates know how to properly format a citation to something with no specified author (thus the HTML comment formatting above).
Do not use |author=none
Do not use |author=unknown, |author=not sure or anything else vague; any implication other than that the source itself did not specify an author is simply a signal to other editors to re-tag it with {{author missing}}.
If you don't know:
Do not use question marks.
Check the source, and add the necessary information, as above.
If the source is a dead link, check archive.org for a backup copy (see your {{citation}}/{{cite xxx}}-type template's documentation for use of |archiveurl= and |archivedate= parameters). If no archive copy is available, use {{dead link}} after the citation, but leave {{author missing}} as well.