Publication requires commercial exploitation
When registering a copyright in the US, the applicant has to declare whether the work has been published or not published. Getting the publication status wrong will render the registration certificate invalid.
How do you know whether you have displayed or published?
Under the Copyright Act, "publication" means "the distribution of copies . . . of a work to the public by sale or other transfer of ownership, or by rental, lease, or lending"; and "[a] public . . . display of a work does not of itself constitute publication." 17 U.S.C. § 101.
In the context of posting an image on the internet, courts have said "Merely posting a digital file . . . on the Internet lacks the element of commercial exploitation" that defines publication. Einhorn v. Mergatroyd Prods., 426 F. Supp. 2d 189, 197 n.45 (S.D.N.Y. 2006) (Kaplan, J.); see also McLaren v. Chico's FAS, Inc., 2010 U.S. Dist. LEXIS 120185, at *12 (S.D.N.Y. Nov. 9, 2010) (Rakoff, J.) (Plaintiff’s "claim that images composing the Collection were posted on her website would not in any event suffice to plead 'publication.'").
A recent decision found that the display of a photograph of the artist Madonna as part of an interview by the photographer for a fanblog did not constitute a publication because "[t]he record contains no evidence that Plaintiff provided the Madonna Photograph to [the fanblog] to reap any commercial advantage." Feingold v. Rageon, Inc., Case 1:18-cv-2055 (July 15, 2020, SDNY) (Opinion at p8, hosted on Mega.nz).