A site’s terms of service may state that you grant certain permissions regarding the content you post, but that’s typically so that they can display it in other people’s feeds. It takes pretty explicit consent to give up or transfer your copyright to another entity. So while you’re granting permission to transmit what you post to others, it would be a really difficult case to make that you have given up your ownership of what you post. For example, if you post a photo you took to Lemmy, you’re granting your instance permission to distribute it across the fediverse, but you still own the photo.
Disclaimer: not a lawyer but have studied copyright law academically.
A site’s terms of service may state that you grant certain permissions regarding the content you post, but that’s typically so that they can display it in other people’s feeds. It takes pretty explicit consent to give up or transfer your copyright to another entity. So while you’re granting permission to transmit what you post to others, it would be a really difficult case to make that you have given up your ownership of what you post. For example, if you post a photo you took to Lemmy, you’re granting your instance permission to distribute it across the fediverse, but you still own the photo.
Disclaimer: not a lawyer but have studied copyright law academically.