The number of weibo users on the mainland fell by 9 per cent last year to 281 million - a first-time drop that comes during a government crackdown on online "rumour-mongers".
The decline contrasts with an increase in mobile instant-messaging services, which analysts said offer better privacy and save people from running into legal trouble for their public remarks on weibo, online chat rooms and other social media websites.
In its half-yearly internet report published yesterday, the China Internet Information Centre (CNNIC) said 37 per cent of users who stopped using weibo last year turned to WeChat, Tencent's mobile instant-messaging service. Tencent and Sina are major weibo providers.
"People are moving to WeChat, which allows people to communicate with only their close friends and they can speak openly," said Wang Chengjun, a web researcher at the City University of Hong Kong.
"Why would people want to continue being careful about their words on a tool meant to disseminate information?"
In September, the Supreme People's Court and the Supreme People's Procuratorate issued a judicial interpretation that anyone would be held criminally liable for false online posts that were viewed more than 5,000 times or shared more than 500 times. Authorities have targeted a number of influential opinion leaders on weibo, with some of them being detained.
The CNNIC report, however, said microblogs' disappointing results were related to competition and the difficulties operators face making money from them.
The report said there were 532 million instant-messaging service users by the end of last year, 64.4 million more than in 2012.