First Authorship: What the Position Signals, Who Decides It, and How Shared First Authorship Actually Works

ICMJE's four authorship criteria (a substantial contribution, drafting or critical revision, final approval, and accountability) settle who belongs on the byline at all. They say nothing about sequence. The Recommendations say the criteria for ordering the byline may vary and are decided collectively by the author group, not by editors. ICMJE sets no formula for it.

In practice, most labs settle order with one of three approaches:

1. Contribution mapping. Write down what each qualifying author actually did, then rank by scope and effort. This is the most defensible method if the order is ever questioned.
2. Role convention. In labs that already have a norm (the person who ran the experiments and wrote the draft is always first, the PI is always last), the mapping step is mostly a formality.
3. Negotiated compromise. When two people did genuinely comparable work, the group either picks one name with a stated tie-breaker (who wrote the draft, who will present the work) or moves to a shared-first designation.

None of these is more "correct" than the others in ICMJE's eyes. What matters is that the group agrees before submission, not after a reviewer or a hiring committee asks.

Source: Manusights editorial synthesis of ICMJE's order-setting guidance, applied as a decision checklist.

Run your own author group through that checklist before the first full draft circulates. For example, a two-person team that mapped contributions and found genuinely comparable work should decide on a shared-first footnote at that point, not after a reviewer asks about the order.

Co-first, joint-first, or "equal contribution" authorship formally marks two or more authors as having contributed comparably, so the single-file byline order does not misstate a genuine tie. Most major publishers show it as a note under the author list ("These authors contributed equally to this work"). The JATS XML tag they use to mark it can flag only one set of authors, so a second tied set, a co-last pair for example, is carried by footnote text alone.

This is not a reason to avoid shared-first designations when the work genuinely was comparable. It is a reason to describe the designation explicitly wherever you list the paper yourself, since the record that matters for tenure and hiring committees will not always do that for you.

Order disputes themselves are outside the scope of a manuscript review. What turns an ordinary order decision into a later dispute is usually a paperwork gap, and three are worth checking before submission.

No contribution statement, so the order has no written justification. A manuscript arrives with a ranked author list and no authorship contribution statement explaining why. If a question comes up post-publication, there is nothing on record beyond the order itself. Journals that require a contributions section flag this at submission; journals that do not still benefit from having one drafted internally.

A co-first footnote that does not match the contribution statement. Two authors are marked as contributing equally in the footnote, but the contribution statement describes clearly unequal roles, one ran the primary experiments and wrote the draft, the other supported analysis. Reviewers and editors read both; a mismatch invites the exact question the footnote was meant to prevent.

The order was set by seniority, not contribution, and nobody wrote that down either way. This is not against any rule. It becomes a problem only when it is discovered later and nobody can explain the reasoning, because the reasoning was never recorded.

Manusights does not decide who goes first. Neither the free scan nor the $39 Full Review checks author order, co-first footnotes, or contribution statements; both read the science in the manuscript. Settle the byline with your coauthors, in writing, and run the scan once it is agreed.