Not true. "can claim" means nothing and "did not know" is not valid defense. Copyright is well protected without any symbols or copyright notice. Content is automatically protected by copyright. With, or without copyright mark you need to fight the one who uses your content without permission.
If you want to make claiming copyright easier, register your unpublished or published work. In US you can do it in U.S. Copyright Office
In EU you can use Datasure in Copyright.eu to get official proof of the date and content of your creations.
liquid99•1h ago
It just means "If you do not mark your work as copyrighted using this symbol, and later sue someone for copyright infringement, you will likely be awarded lesser damages. This is known as the “innocent infringement” defence."
nabla9•1h ago
If you want to make claiming copyright easier, register your unpublished or published work. In US you can do it in U.S. Copyright Office
In EU you can use Datasure in Copyright.eu to get official proof of the date and content of your creations.
liquid99•1h ago