Habitual content - texts, photos, videos, design and programs - are works. The creators of works own copyrights: indicate their name, receive money for publication and some others under Art. 1255 of the Civil Code of the Russian Federation.
To be considered an author, you do not need to draw up special documents - Art. 1259 of the Civil Code of the Russian Federation. Evidence will be needed only if someone stole the content or if there is a dispute about authorship.
Article on compensation for copyright infringement
You can prove that you are the author by any means - this is how the Supreme Court explained in paragraph 110 of Resolution No. 10 of April 23, 2019. But it is better to record the authorship and date of creation in advance.
We have collected well-known methods of fixing authorship on content and programs. Look what happened.