BEIJING/HONG KONG, Jan 20 (Reuters) - TikTok owner ByteDance saw its total revenue grow by 70% year on year to around $58 billion in 2021, according to two people familiar with the matter, slower growth than a year earlier as China tightens its regulation of big tech companies.

The figures were disclosed to a small group of employees at an internal meeting of the social media giant this week, according to the people.

In 2020, the Beijing-based company's total revenue grew by over 100% to $34.3 billion https://www.reuters.com/business/tiktok-owner-bytedances-2020-revenue-soars-net-loss-45-bln-memo-2021-06-17, Reuters has reported.

Chinese tech companies from Tencent Holdings to Alibaba Group have reported slowing growth amid a wide-ranging crackdown by the country's regulators who have rolled out new rules https://www.reuters.com/technology/china-require-certain-firms-undergo-cybersecurity-reviews-before-pursuing-2022-01-04 governing how they operate and interact with their users.

Tencent in the third quarter posted its slowest revenue growth since it went public in 2004.

ByteDance retained its second-ranked position in China’s online advertising market last year, with a market share of 21%, according to a recent report published by researcher Interactive Marketing Lab Zhongguancun.

The number one position was still held by e-commerce giant Alibaba, and third place went to gaming giant Tencent, according to the report.

The overall growth of online ad sales in China declined to 9.3% in 2021 from 13.8% a year earlier, the report says.

Tech news website The Information last November reported that ByteDance's 2021 revenue was on track to rise about 60% to 400 billion yuan ($63.07 billion).

ByteDance is one of the world's biggest private tech companies with recent trades in the private-equity secondary market valuing it at about $300 billion, Reuters has reported.

Following Beijing's antitrust efforts, ByteDance has recently been downsizing its powerful investment arm https://www.reuters.com/technology/chinas-bytedance-says-has-reorganized-strategic-investment-team-2022-01-19.

In November, ByteDance reorganized itself into six business units in its biggest organizational change since ByteDance founder Zhang Yiming said in May he would step down as CEO.

Besides TikTok, ByteDance's other apps include its Chinese equivalent Douyin, news aggregator Jinri Toutiao and video-streaming platform Xigua.

In 2021, users spent approximately $2.3 billion in TikTok and the iOS version of Douyin, a 77% jump year-over-year, according to app tracker Sensor Tower. ($1 = 6.3419 Chinese yuan renminbi) (Reporting by Yingzhi Yang and Xie Yu; Editing by Brenda Goh and Elaine Hardcastle)