'Happy Birthday to You' was under copyright for nearly a century before a court ruled it wasn't.

The melody of “Happy Birthday to You” dates back to an 1893 song called “Good Morning to All,” written by sisters Patty and Mildred Hill. For decades, a music publisher held copyright claims over the “Happy Birthday” lyrics specifically, and film and TV productions reportedly paid licensing fees just to have characters sing it on screen, which is part of why the song is often noticeably absent or replaced in movies and shows.

In 2015 and 2016, a federal court ruled that the copyright claim was invalid, finding that the publisher had never actually held rights to the lyrics. The song was declared to be in the public domain, meaning that after roughly 80 years of being technically restricted, the world’s most commonly sung song became free for anyone to use without paying royalties.