A copyright notice is the small line—© 2026 Acme Corp.—that announces who owns a creative work and when it went out into the world. For works first published in the United States on or after March 1, 1989, notice is optional; for works published before that date it was mandatory, and a missing or defective notice could dump a work into the public domain on the day it appeared. This UpLaw article dissects the three statutory elements of a proper notice, walks the governing sections at 17 U.S.C. §§ 401–406, and explains the three-era timeline that makes the publication date the single most important fact in the analysis. It shows how notice still forecloses an infringer's innocent-infringement plea to protect statutory damages under § 504(c), where notice belongs on books, records, film, software, and websites, and how derivative, collective, government, and restored foreign works each bend the rules. It closes with a modern marking checklist, a field method for reading old notices, and a deep set of cross-references into the UpLaw copyright library.