China has disrupted WhatsApp in a censorship drive ahead of the government's Communist Party meeting next month.
It has only been accessible through virtual private networks (VPNs) at times - but even some of them are being blocked.
Other social media platforms, which people in the West use every day, are also banned in mainland China.
Instead they're replaced by other ones which the government can monitor.
So what social media platforms are Chinese people able to use?
WeChat started off as pretty much a direct replica of WhatsApp, but it's now used for a lot more than just messaging and calling.
You can use it to pay for things, do your online shopping and play games.
It was created by Chinese company Tencent and there's also a feature where you can record a message which is then picked up by a random person - sort of like throwing a message in a bottle in the sea.
But the price its hundreds of millions of Chinese users pay for using it is that all their information is shared with the government.
Twitter has been blocked in China since it was partly blamed for helping to organise a protest in 2009.
That's when Weibo was set up instead and it basically does the same job - you have 140 characters to get your thoughts out.
But it's used differently to Twitter as people tend to post more about their personal and family lives rather than argue about politics.
Although this could partly be down to worries about censorship, it's also because the culture isn't one where people talk about these things in real life - so that translates into the online world too.
Baidu provides a lot of the same services online as Google, which is also banned in China.
But it also has Reddit-style forums called Baidu Tieba and a Wikipedia-style online encyclopaedia.
And like Google, it's investing a lot into AI and self-driving cars.
But the Chinese authorities are investigating Baidu, along with Weibo and WeChat, in an attempt to bring them under even more control.
QQ is a messenger platform owned by Tencent, the same company that owns WeChat - in the same way that Whatsapp is also owned by Facebook.
So they're not really direct rivals to each other but do quite a lot of the same things.
The main difference is that QQ, like Facebook messenger, started as a desktop app rather than a phone app.
You also don't need a phone number to use QQ, which means younger people who don't have a phone yet can use it to message each other.
Youku is China's main site where anyone can upload their own videos - but they are all monitored by the Chinese government and anything criticising the Communist Party is taken down.
It also streams Netflix or Amazon-style original TV shows.
And there are famous "Youkuers" who can make millions of dollars, mostly from directing their users to buy stuff from Alibaba.
That's the Chinese version of Amazon or eBay - which also just happens to own Youku too.