The adoption of the new Online Safety Code brings an end to the era of social media self-regulation, Coimisiún na Meán has said.
The media regulator formally adopted the code following the conclusion of an assessment by the European Commission.
"The code sets binding rules for video-sharing platforms to follow in order to reduce the harm they can cause to users," Online Safety Commissioner Niamh Hodnett said.
"We will work to make sure that people know their rights when they go online and we will hold the platforms to account and take action when platforms don't live up to their obligations," she added.
The rules will apply to video-sharing platforms that have their EU headquarters in Ireland.
The code will be legally binding, and companies will face fines for breaches of up to €20 million or 10% of a platform's annual turnover, whichever is greater.
The general obligations contained in the code will apply from next month and platforms will have an implementation period of up to nine months for certain detailed provisions, which require IT build, to come into compliance.
From next month, the videos covered include content that impairs the physical, mental, or moral development of minors; incitement to hatred or violence; and child sexual abuse material.
The more detailed provisions, which will have a nine-month lead-in period, will cover content including cyberbullying, the promotion of self-harm, suicide, eating disorders or dangerous challenges; as well as pornography and extreme or gratuitous violence.
Platforms will have to use age assurance systems and provide parental controls.
Reddit not yet included
In December 2023, Coimisiún na Meán designated ten video-sharing platforms that will be covered by the Online Safety Code.
They were Facebook, Instagram, YouTube, Udemy, TikTok, LinkedIn, X, Pinterest, Tumblr and Reddit.
The code will be applied to nine of the ten platforms, with An Coimisiún saying it has not reached a determination in respect of Reddit.
Although Snapchat is incredibly popular among young people, it is not included on the list of designated platforms.
This is because it does not have its EU headquarters in Ireland.
Asked about regulating Snapchat, Coimisiún na Meán has said it will be working closely with its regulatory counterparts in other EU member states to hold platforms to account for how they keep their users safe.

Recommender systems not covered
Recommender systems are algorithms that determine what social media users see based on personal data such as search history, past purchases, age and location.
Campaign groups and researchers have warned that these algorithms can be 'toxic' and often result in inappropriate content appearing in users' feeds promoting things like hate, extremism, eating disorders and self-harm.
These algorithms are not covered by the Online Safety Code.
Dr Johnny Ryan, a senior fellow with the Irish Council for Civil Liberties (ICCL), said this was a disappointment.
"We should have seen clear steps to intervene and stop the toxic algorithms that push self-loathing and suicide into our children's feeds but there is absolutely nothing about that in the code," Dr Ryan said.
Coimisiún na Meán has said that while it recognises that recommender systems can have harmful impacts on users, especially children, it will be best able to tackle the potential dangers of these systems through its implementation of the EU's set of online safety rules, the Digital Services Act (DSA).
The Online Safety Code will run alongside the DSA and form part of Ireland's overall internet safety framework.
Ireland's code does not specifically cover disinformation but Coimisiún na Meán has said that when disinformation crosses the threshold of being illegal content covered by the DSA, or regulated content under the code, platforms must prevent it being uploaded or shared.
"With the adoption of the Online Safety Code, all the elements of our Online Safety Framework are now in place," said Executive Chairperson of Coimisiún na Meán, Jeremy Godfrey.
"Our message to people is clear: if you come across something you think is illegal or against a platform's own rules for what they allow, you should report it directly to the platform. Our contact centre is available to provide advice and guidance to people if they need help," Mr Godfrey said.
Minister for Media Catherine Martin welcomed the adoption of the Online Safety Code.
"It introduces real accountability for online video sharing platforms and requires them to take action to protect those that use their platforms, including by having robust complaints handling procedures and introducing effective age-verification," Ms Martin said.
Taoiseach Simon Harris also said the new code marks the end of an era of social media self-regulation.
"The Online Safety Code sends a strong message to social media platforms that they will be held accountable for how they protect those who use their sites from harmful video content," Mr Harris said.