This is a story about friendship, technology, commerce, sex, silliness, surveillance, entrepreneurship and messages in bottles. It is a story about ordinary people, including me, maybe even you, and definitely 19 others within a radius of one kilometre of the desk at home on which I am writing this. It is the story of China’s killer app WeChat.

WeChat, weixin 微信 or ‘micro-letter’ in Chinese, boasts 650 million monthly active users (out of 1.1 billion registered accounts). That’s less than those on the world’s most popular messaging app WhatsApp (900 million) and on Facebook Messenger (800 million). But those 650 million – and the number is growing rapidly – aren’t just telling each other what train they’re on, sharing photos of their breakfasts, flirting, or organising or conducting a meeting, though they do all of this too, of course. They are living the WeChat life.

Users, in China at least, can order and pay for a taxi; donate to their favourite charity; send DIY postcards from whatever city they’re in; transfer money to a friend; find their nearest petrol station; check in for a flight; search a library catalogue for a book; shop; pay off a credit card; book a doctor’s appointment; follow the official accounts of celebrities ranging from Fan Bingbing to John Cusack; buy movie tickets; keep up with the Communist Party line via the People’s Daily (WeChat’s most heavily subscribed official account); check the points on their driver’s licence; top up their mobile accounts and find restaurant reviews, in some cases discovering how many people are queuing for tables before adding their names to the list. A Chinese toy company has even created a cute little Bluetooth-enabled plush toy (‘Mon-Mon’) based on a popular WeChat emoji that a parent can use to send voice messages or even pre-recorded bedtime stories to their children while away – and all a child has to do to reply is press the creature’s belly and talk. WeChat is, as David Pierce wrote in Wired magazine, ‘The Everything App’.

Each user has both a personal QR code and an inbuilt scanner that makes for a seamless exchange of contacts. Not so long ago in China, it was de rigeur for the newly introduced to exchange name cards. Today you are less likely to be asked ‘you mingpian ma?’ (‘do you have a name card?’) than ‘ni sao wo haishi wo sao ni?’ (‘will you scan me or shall I scan you?’).

Once connected, wherever you are in the world, you can chat individually or in groups via text, voice messages, or free Skype-like voice or video call. You can of course also send photos, songs, news items, emojis and ‘stickers’ as well. I mainly use WeChat in my work with Chinese film directors and producers for whom I translate movie subtitles; pay for cabs when I’m in China; and keep in touch with Chinese and a growing number of other friends too. I admit I also occasionally get lost down the rabbit hole of sticker wars: someone sends me one of pigs waving out of a window, I raise them a lipsticked, winking Kim Jong Un, and they put a dancing cat on the table.

If you don’t have friends, no worries. WeChat will find you some. Check out the people nearby and send out an exploratory ‘hi’ (which they can answer, ignore or take as a reminder to fix their privacy settings). Or choose the ‘shake’ function: physically shake your phone (producing a satisfying sound like that of maracas) and see who is shaking theirs at the exact same time. In my limited experience, incidentally, it is always someone in the Middle East. Perhaps you would prefer to send out or collect a ‘message in a bottle’. And if that’s all too much, you can just play games.

WeChat has an enormous market in China alone. One-fifth of the world’s population is Chinese and mainland China has more than twice as many internet users as the US (674 million as compared with 281 million, according to 2015 statistics). But already, one out of every four users of WeChat is non-Chinese, and the company has its sights set on world domination. It has enlisted celebrities including Barcelona footballer Lionel Messi and Bollywood stars Varun Dhawan and Parineeti Chopra to promote it into European, South American, South Asian and other markets.

WeChat supports nearly 20 languages including English, Spanish, Hindi, Indonesian and Russian. In July last year, Apple CEO Tim Cook said that of the approximately 8,500 third-party apps available for the Apple Watch, WeChat, along with Twitter and LINE, was among the most-used. Australia already has at least one company (HiWeChat) that specialises in helping businesses market into China using WeChat.

According to the Wall Street Journal, while Facebook is certainly trying, ‘it won’t be simple for Facebook or others to copy WeChat’s success.’ David Pierce is even more categorical: ‘Many apps will try to replicate what WeChat has done, and all (or all but one) will fail.’

The reason is because WeChat’s ‘mobile-first’, PC-free development model is unique. In 2011, the Chinese media, communications and internet giant Tencent, which Forbes now rates number 11 in the world for innovation, created WeChat in part to give users a way of avoiding costly text messages. Two years later, it introduced a payment system, and things really began to take off.

Forbes has described WeChat variously as ‘an entire ecosystem’ and ‘a rainforest-like entity that supplies energy to many other apps and services’. WeChat makes it easy for other businesses and app developers to get on board by providing an open application programming interface (API) for them to use. The tech and business analyst Connie Chan has written about how WeChat pioneered the model of “apps within an app”. She notes that over 10 million lightweight apps (what WeChat calls ‘official accounts’) ‘live inside WeChat, much like webpages live on the internet’. This makes WeChat, she says ‘more like a browser for mobile websites, or arguable, a mobile operating system – complete with its own proprietary app store.’

WeChat’s expansion into every aspect of life in China, which has been in tandem with the rise of China’s middle class, and the speed at which it is extending itself into the rest of the world is a business and technology success story. But it also raises uncomfortable questions.

Some of the concerns are about its monopoly, or near-monopoly power – similar to those raised in relation to other establishment ‘disruptors’ like Google and Facebook. Others are to do with the fact that WeChat operates within a country ruled under a dictatorial, one-party system that displays little tolerance for dissenting views or simple outspokenness on topics it considers sensitive. One reason for the slow decline in the popularity of Weibo was that it was easy for the government to monitor and censor.

A number of dissonant voices have moved to WeChat. Its accounts work in a less public manner: only their subscribers and those to whom they forward posts will see what they have written. No one in China is so deluded as to think that the government is not monitoring WeChat to the best of its ability, which in the field of surveillance is considerable. As with Weibo and the Internet in general, government censors use algorithms that pick up sensitive words and banned topics. These include Tibet, corruption, the forced demolition of houses, the massacre of pro-democracy protestors in Beijing in 1989, ‘petition’, the mistresses kept by officials and even ‘constitutionalism’. But the censors are getting more clever. WeChat has a voluntary reporting system for ‘illegal content’; when something disappears, the message implies that it was one’s fellow users who were offended by it.

Certainly, the NSA is also watching what you say on Facebook, Twitter and email (or at least to whom you’re saying it), and this should concern us all. But to date, only China jails people who pass on ‘false information’ (which might, in fact, be true, but inconveniently so) that is then forwarded 500 times or viewed 5,000 times.

It will be interesting to see how this works in the context of WeChat’s expansion internationally. Few users in Australia, Europe, the US or elsewhere are likely to tolerate political censorship on a messaging-and-more platform. It does seem there is greater tolerance when it comes to posts in English; it’s something to watch in any case. It just may prove impossible to impose closed values on an open market. And as one official has been reported as observing, there’s got to be at least one place where people can let off a bit of steam, and WeChat might be it.