Large tech companies, such as Google and Meta, will have to take action on deepfakes and fake accounts - or risk facing huge fines.
Deepfakes are videos using a person's likeness to portray them doing something they never did.
New EU regulation, supported by the Digital Services Act (DSA), will demand tech firms deal with these forms of disinformation on their platforms.
Firms may be fined up to 6% of their global turnover if they do not comply.
The strengthened code aims to prevent profiting from disinformation and fake news on their platforms, as well as increasing transparency around political advertising and curbing the spread of 'new malicious behaviours' such as bots, fake accounts and deepfakes.
Clubhouse, Google, Meta, TikTok, Twitter and Twitch are among the 33 signatories to the enhanced code and worked together to agree the new rules .
Firms who have signed up to the code will be compelled to share more information with the EU - with all signatories required to provide initial reports on their implementation of the code by the start of 2023.
Platforms with more than 45 million monthly active users in the EU will have to report to the Commission every six months.
Nick Clegg, Meta's president of global affairs, wrote on Twitter: "Combating the spread of misinfo is a complex and evolving societal issue".
"We continue to invest heavily in teams and technology, and we look forward to more collaboration to address it together."
A Twitter spokesperson said the company welcomed the updated code.
"Through and beyond the Code, Twitter remains committed to tackling misinformation and disinformation as we continue to evaluate and evolve our approach in this ever-changing environment," a statement said.
Google did not respond to a request for comment.
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