Authorship · Reference
What is co-authorship?
Co-authorship is the sharing of formal authorship of a research output between two or more people, each of whom has made a contribution that meets the relevant authorship criteria and each of whom shares accountability for the work.
The step most authors miss
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What co-authorship means
A co-author is simply one of several authors of the same output. Co-authorship is the normal state of modern research: most papers in the sciences have multiple authors, and team sizes have grown steadily as research has become more collaborative and methodologically specialised.
Crucially, being a co-author is not a courtesy. Every co-author should meet the same authorship criteria as any other author — a substantial intellectual contribution, involvement in drafting or critically revising the work, approval of the final version, and willingness to be accountable for it. Listing someone who did not contribute substantively (a "gift" or "honorary" author) and omitting someone who did (a "ghost" author) are both recognised forms of authorship misconduct.
Co-first authorship and shared authorship
Where two or more authors have contributed equally to the work, journals allow them to be designated co-first authors (or joint first authors), usually marked with a symbol and a footnote stating that the authors contributed equally. The same arrangement exists at the other end of the byline as co-senior or co-last authors. Shared first authorship is common in large team science and is intended to give fair recognition where a single ordering would misrepresent two equal contributions — although tenure and hiring committees still vary in how they weight it.
How co-authors share responsibility
All co-authors share collective responsibility for the integrity of the published work, and each author should be able to identify which co-authors are responsible for which parts. This is where a structured contribution statement helps: rather than every co-author implicitly vouching for the whole paper, a CRediT statement records what each person actually did, making both credit and accountability specific and machine-readable.
Co-authorship etiquette and disputes
Most co-authorship problems are preventable by agreeing, early in a project, who will be an author, in what order, and on what basis. Disputes commonly arise from late additions, supervisors expecting automatic inclusion, contributions that grow or shrink during a project, and unclear expectations between collaborators. COPE provides guidance and flowcharts for resolving such disputes, and many institutions now ask research groups to record an authorship agreement at the outset.
Key facts
At a glance
- Definition: being one of two or more authors of the same output
- Each qualifies: every co-author should meet the authorship criteria in full
- Co-first: equal contributors marked as joint first authors with a footnote
- Accountability: co-authors share responsibility for the integrity of the work
- Misconduct: gift, guest and ghost authorship are all improper
- Best practice: agree authorship and order at the start of a project
Common questions
FAQ
What is the difference between an author and a co-author?+
There is no difference in kind — "co-author" simply means one of several authors of the same work. Every co-author should meet the same authorship criteria and shares the same accountability for the published output.
What is co-first authorship?+
Co-first (or joint first) authorship is when two or more authors have contributed equally and are designated as shared first authors, usually marked with a symbol and a footnote stating that they contributed equally to the work.
Does being a co-author mean I am responsible for the whole paper?+
Co-authors share collective responsibility for the integrity of the work, and each should be able to identify who is responsible for which parts. A CRediT contributor-roles statement makes each person’s specific contribution explicit.
Can someone be listed as a co-author as a favour?+
No. Adding someone who has not made a substantial contribution is "gift" or "honorary" authorship and is considered authorship misconduct, just as omitting a genuine contributor ("ghost" authorship) is.
How should co-authors decide author order?+
Order conventions vary by discipline, but the fairest approach is to agree order — and the basis for it — at the start of the project and to revisit it if contributions change substantially.
