Move over, Weibo. Here comes WeChat. Weibo, China's microblogging platform that's a hybrid of Twitter and Facebook, was the hot place to be as recently as last year. Now, marketers are clamoring to engage with WeChat and the 300 million users it's amassed in just two years.

"Everyone is using WeChat, so marketers are wondering how can they use it in their communications," said Sophia Ong, the executive at WeChat's parent company, Tencent, who helps marketers navigate the internet giant's myriad platforms. "They know it's very influential, everyone is using and sharing it. And slowly some brands are coming out with official WeChat accounts."

China's newest digital darling is a mashup of several existing applications, with a few fun features like "Shake Shake" and "Drift Bottle." WeChat users trade text, audio and video messages with friends over mobile-data networks. There's a popular group-messaging function and newly unveiled live-chat capabilities. Photos can be posted on an Instagram-like "Moments" page, while "Look Around" identifies other WeChat users nearby. There's also a QR-code reader.

"We love to use all the social connections because different people want to connect with us in different ways," said Ben Wilson, marketing director for Reckitt Benckiser in China, talking about Durex's online-communication strategy. "On WeChat, you can be a little more personal."

One big reason for WeChat's stellar growth is that contact lists are linked to Tencent's QQ instant-messaging platform, which has more than 700 million active accounts. But users can also make friends through Drift Bottle -- picking (and sending) notes at random from mobile cyberspace. Shake Shake connects users who happen to be shaking their smartphones at the same time. It's a quick way to swap contact details. Pete Blackshaw, global head of digital at Nestle, recently tweeted about having a major WeChat "shake-fest with friends and colleagues."

Should Twitter, Facebook, Instagram, WhatsApp, Skype and others be worried? Considering that WeChat's stellar growth has come in large part from QQ, maybe not. But Mark Natkin, a technology analyst in Beijing, says the West can learn a thing or two from WeChat.

"They can be a little more aggressive in adding more social features more quickly," he said. "In the earlier stages, any user you mentioned WeChat to would say, "Oh, Shake Shake! I can go out and meet people I don't know.' It was something interesting and unusual. And that got a lot of buzz going, getting people to try it."

Out of all the Chinese digital products, WeChat is perhaps the best positioned for global expansion. Launched in January 2011 as Weixin ("way-sheen"), it was rebranded in April 2012 with the globally palatable moniker WeChat. It's offered in languages from English to Turkish to Arabic. Tencent says WeChat is Apple's No. 1 social-networking app in Southeast Asian countries like Thailand and Malaysia, but also in Saudi Arabia. It's being promoted in Indonesia, India, Argentina and Australia.

Blog TechNode quoted WeChat Product Director Zeng Ming as saying that Europe and the States is its next challenge.

Tencent has been picky about who's allowed to do WeChat marketing. "Every time we talk to clients, we say you have to commit to doing social CRM," Ms. Ong said.

How Marketers in China Are Using WeChat

Durex uses WeChat in a culture where public discussion about private issues is uncommon. Fans curious about love, sex and relationships get a response from a real person, even at 2 a.m. "We try to be there when you expect a friend to be there for you," said Ben Wilson, marketing director for Reckitt Benckiser in China. Each week, a "newsletter" of Q-and-As is sent to Durex's WeChat friends.

Tens of thousands flocked to Nike's Festival of Sport last summer, sampling everything from skateboarding to football to golf.

AKQA created a badge-collection system using WeChat's QR-code scanner, replacing a paper passport. Fans completing certain challenges could win a chance to meet stars like LeBron James.

London Olympics competitions largely took place in the middle of the night in China. So Intel hired two celebrity hosts to provide audio updates three times a day. Each morning, they summarized the previous night's events. At lunchtime, fans were given an Olympics or Intel-related contest question. In the evening, the hosts announced winners along with another sports update.

To reach customers through music, Starbucks asked fans: "How are you feeling today?" They responded with an emoticon, and Starbucks answered with a song to match the mood. The chain added 270,000 WeChat friends over the four-week campaign. "We don't just push offers at you," said Marie Han Silloway, Starbucks' marketing chief for China. "We start a personal conversation."