What is a copyright notice? How do I put a copyright notice on my work?

A copyright notice is optional and advises would-be copiers who the copyright owner is. Any form of notice can be used — a standard approach is to use the © symbol with a name and date. On a webpage, the © symbol is made with ©; on a keyboard, try ALT+G (Mac).

“A copyright notice is an identifier placed on copies of the work to inform the world of copyright ownership. The copyright notice generally consists of the symbol or word “copyright (or copr.),” the name of the copyright owner, and the year of first publication, e.g., ©2008 John Doe. While use of a copyright notice was once required as a condition of copyright protection, it is now optional. Use of the notice is the responsibility of the copyright owner and does not require advance permission from, or registration with, the U.S. Copyright Office.”
— U.S. Copyright Office