Numerous young people lined up looking at phones.

You've likely used several social networks, but have you heard of these? Image source: Getty Images.

Social media has become a worldwide phenomenon over the last several years and has changed the way we communicate. According to a recent report by We Are Social, there are over 2.8 billion social-media users -- a full 37% of the global population. That number is still growing, having increased 21% during 2016.

In the U.S., social media is dominated by a handful of well-known networks, but outside the States, other platforms are king. Let's look at some of the largest social-media sites that most U.S. users have never encountered. 

Asian girl using smartphone at cafe

Weibo is China's Twitter. Image source: Getty Images.

4. Weibo: 361 million monthly active users

Weibo Corporation (NASDAQ:WB) is a spinoff of Chinese internet giant SINA Corporation (NASDAQ:SINA). It's been called China's Twitter, and is the country's third largest social-media site. User engagement has seen impressive growth since the company debuted its Stories feature in April, which allows users to share photos and short videos that disappear in 24 hours. The recent addition of short video has been a particularly strong usage-driver: Daily views grew 159% year over year in the most recently reported quarter. 

Weibo has been working with smartphone makers to optimize its app on mobile devices, reducing memory and power consumption while increasing response times. Those moves have been a hit with users, which grew 28% over the prior-year quarter. More users means greater revenue, and in the most recent quarter, sales of advertising grew 72% year over year as advertisers continued to flock to the platform. Revenue from small to medium-sized enterprises and key accounts grew at an even faster clip, up 79% over the prior-year quarter. 

Three young people looking at smartphones, oblivious to each other.

Qzone is China's largest traditional social network. Image source: Getty Images.

3. Qzone: 606 million monthly active users 

Tencent's (NASDAQOTH:TCEHY) Qzone is China's largest traditional social-networking site, and it makes money through in-platform purchases, subscriptions, and games. Users can write blogs, post updates, share photos, listen to music, and watch videos. Many also purchase a variety of digital accessories, backgrounds, and templates to customize their home pages.

Use of the premium "Canary Yellow Diamond" level, which provides access to every service for free -- or at a discounted rate -- has been slowing. In Qzone's most recent quarter, users fell 3% year over year, and the user base has languished since 2013. Revenue from all the company's social networks for the quarter came to $1.9 billion, which was 23% of the company's total revenue. 

Three smiling people looking at each others smartphones.

QQ provided texting when data plans were still expensive. Image source: Getty Images.

2. QQ: 850 million monthly active users

Tencent's QQ is a legacy text-messaging app that filled the void when texting via cellphones in China was still costly. The service has an extremely engaged user base that has been in slow decline. The number of younger users is increasing, however. More than 60% of QQ's users were born after 1990, providing a sought-after demographic for advertisers.

QQ is hoping to re-energize it's former flagship service by targeting the tech-savvy generation with entertainment-oriented features and user favorites such as animated video stickers and music-streaming services. Advertisers have been going high-tech, using augmented-reality ads to attract these younger users.

In the most recent quarter, QQ's users fell 5% over the prior-year quarter. Online advertising from all sources for the quarter was $1.5 billion, accounting for 18% of the company's revenue. 

Group of people using mobile phones.

WeChat provides so much more than messaging. Image source: Getty Images.

1. WeChat (Weixin): 963 million monthly active users

Tencent's WeChat is China's most popular mobile messaging app, similar to WhatsApp. WeChat can be used to send text, voice, and photos, and it also offers a curated newsfeed. WeChat and Weixin are two versions of the same app, though Weixin -- "micro letter" -- can only be used by consumers in China. Weixin has integrated location-specific functionality and many features that its international counterpart lacks.

The app allows users to hail rides, order food delivery, make payments, and play online games, all without leaving the app. Online ads and games produce the bulk of the revenue, and business is booming.

In its most recent quarter, WeChat's user base grew 20% year over year, while revenue jumped 59% over the prior-year quarter. Tencent's online-games segment contributed $3.5 billion of the company's total $8.4 billion in revenue. 

Danny Vena has no position in any of the stocks mentioned. The Motley Fool recommends Sina and Weibo. The Motley Fool has a disclosure policy.