Singapore and Malaysia are using Simplified Chinese Characters officially. Taiwan (Speak Mandarin), Hong Kong (Speak Cantonese) are still using Traditional Chinese Characters officially.
China (Speack Putonghua) using Simplified Chinese. South of China especially Canton Guangzhou speak Cantonese use Simplified Chinese.
*HOWEVER, there are more than 100’s different dialects in different provinces which 3/10 Chinese who they cannot communicate with Putonghua with each others.
“As many as three in 10 of China’s 1.3 billion population are unable to communicate in Putonghua, China’s Education Ministry said during an annual event to promote the official language.” source from SCMP