Next week Tumblr will start blocking pornographic posts. Next year a new law will force porn sites to verify that people watching in the UK are over 18. It’s the first attempt to restrict access to porn online. It’s not yet clear how age verification will work and the social media platforms’ own rules about what is and is not allowed seem to change all the time. US porn star Bonnie Rotten and the UK’s Zara DuRose discuss the issues they face publicising their work, while the BBC’s Thomas Fabbri and Kim Gittleson explain what lies behind the bans.