ICMJE criteria on authorship stipulate
- Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; AND
- Drafting the work or revising it critically for important intellectual content; AND
- Final approval of the version to be published; AND
- Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
In addition to being accountable for the parts of the work he or she has done, an author should be able to identify which co-authors are responsible for specific other parts of the work. In addition, authors should have confidence in the integrity of the contributions of their co-authors.
Authorship is ultimately confirmed by signing the JMIR License to Publish (see Where can I find the publication forms for authors and where do I submit them?).
If one author refuses to sign or cannot be tracked down to sign, he/she is likely not meeting all authorship criteria (although special rules are applied if an author is incapacitated or passed away). See How to change authors after peer-review but before publication if authorship changes are required at this stage.
There is no maximum number of authors for a submission. However, if the number of authors is quite large (ie, 15+) please do consider that you may also list authors as "study collaborators" (sometimes called non-author contributors), i.e. as members of a group (collaborative) author (What is a group author (collaborative author) and does it need an ORCID? and What are "collaborators" and where should they be listed?). Only authors have to sign the form, not individual collaborators (members of a group author).
Contributors who meet fewer than all 4 of the above criteria for authorship should not be listed as authors, but they should be acknowledged in the Acknowledgements section in the manuscript (before the references). Examples of activities that alone (without other contributions) do not qualify a contributor for authorship are acquisition of funding; general supervision of a research group or general administrative support; and writing assistance, technical editing, language editing, and proofreading.