Never co-author articles or have co-authors. They will steal your data and list your papers as their own even though you are first author. Publish on your own if you can with as few references as possible, then your article is elegant and novel. Einstein did it like that! :)

Nowadays, most articles in science have more than one author, in high-energy physics even several hundred or several thousand authors. See these previous discussions on co-authorship:

https://www.researchgate.net/post/Opinions_on_coauthoring

https://www.researchgate.net/post/How_to_Choose_a_Co-author_for_your_scientific_article

https://www.researchgate.net/post/Address_the_ethics_in_authorship_claims_of_research_publications

And her are discussion about the number of authors:

https://www.researchgate.net/post/What_do_you_think_about_multiple_author_papers

https://www.researchgate.net/post/What-do-you-think-about-articles-where-the-list-of-coauthors-is-bigger-than-the-article-itself

https://www.researchgate.net/post/Group_Authorship_is_there_a_minmum_and_maximum

https://www.researchgate.net/post/Is_there_a_limit_to_the_number_of_authors_on_any_scientific_publication_regardless_of_disciplineWhat_is_the_number_of_restrictions_if_there_are_any

https://www.researchgate.net/post/How-many-maximum-number-of-authors-are-enough-in-a-research-paper

https://www.researchgate.net/post/Mesmerizing_list_of_authors_5_154_in_one_article_research_break_through_is_a_group_activity_but_do_we_need_to_include_whole_community

https://www.researchgate.net/post/What_do_you_think_about_single_author_paper

https://www.researchgate.net/post/Single_author_papers_vs_multiple_ones_which_ones_have_more_value

https://www.researchgate.net/post/Solo_author_vs_multi_authors_papers_which_is_more_reliable

The basic criteria include the original contribution of the co-authors to the study or the research work. The research supervisor and other members of the research advisory committee may be given the co-authorship subject to their level of contribution/guidance to the research work. Giving co-authorship to those who don't contribute really is an unethical practice.

Hello Muazzam Sheriff Maqbul

My suggestion is that you should include authors who fulfil all the criteria of the International Committee of Medical Journal Editors. Many journals say this specifically but even if they are more relaxed, I would still follow these conventions.

With these considerations, I have got the number of authors from 20 to 6 on most occasions in recent times.