Though everyone’s original artwork is automatically protected by copyright once it’s completed (paint on to canvas, ink to paper, etc.), I routinely register my art with the United States Copyright Office (USCO) before displaying, selling, licensing, or sharing it with friends and my social media network.
Here’s how I marked my posted art:
Registered Copyright © [year of first publication] + my name + web URL or social media handle + specifications of the artwork with title, medium, dimensions, etc. + my issued copyright Certificate of Registration number + other information (if any) + [Licensed artwork].
Julie Drew wrote, “I embed my name in my image in a watermark before posting online.” This is a great idea! You could even create a stylized watermark to match the artwork.
If a party has my authorization to display my art, I require them to label it as “Licensed artwork,” rather than “Used with permission.” Using legal terms like “licensing,” presents artwork in a more professional manner.
How do you prove that you created your art piece? You simply register it with the USCO! If you register your artwork’s copyright before publication or within five-years of first-publication, you’re granted “presumptive proof” that your copyright and the facts stated in the copyright registration application are all valid. See page 7 of http://www.copyright.gov/circs/circ01.pdf (17 U.S. Code § 410(c)). Using the Poor Man’s Copyright (mailing a print copy of your art in a SASE) is not a substitute for registration and has no legal effect in US copyright law. See https://www.copyright.gov/help/faq/faq-general.html#poorman