It vowed to impose a duty of care to ensure that all companies have systems in place to react to concerns over harmful content and improve the safety for their users, the government said.
“As the internet continues to grow and transform our lives it is essential that we get the balance right between a thriving, open and vibrant virtual world, and one in which users are protected from harm,” Digital Minister Nicky Morgan and Interior Minister Priti Patel said in a joint statement.
The duty of care will apply to platforms on which user-generated content is shared, for example through comments, forums or video sharing, it said on Wednesday in its response to a consultation.
Policy will be developed to offer a higher level of protection for children than adults, the government said.
It said it was minded to make broadcast and telecoms regulator Ofcom responsible for policing the new regime.
Britain proposed new online safety laws last year that it said would be the toughest in the world.
Former Prime Minister Theresa May said at the time she would put a legal “duty of care on internet companies to keep users safe online”. Companies would face big fines, with bosses also held personally accountable, the government said then.
Governments globally are wrestling over how to better control content on social media platforms, often blamed for encouraging abuse, the spread of online pornography and for influencing or manipulating voters.