Introduction
Although there is a general perception that adolescent social media use is a global phenomenon, there is a scarcity of data on patterns and preferences of social media use among youth in low- and middle-income countries. We here describe self-reported prevalences and perceived effects of social media use in a school-based sample of Brazilian adolescents.

Methods
We analyzed cross-sectional data on 7,113 adolescents aged 14 to 16 years-old enrolled in 101 public state schools between 2018 and 2019 in Porto Alegre, Brazil. 

Results
Among the 7,113 with complete data for analyses, 54.9% were female, and 60.6% reported their skin color as white. At least one social media platform was used by 97.7% of adolescents everyday, and 64.7% reported being online “almost constantly”. YouTube and WhatsApp were the most popular platforms. Most participants perceived the effect of social media use on their lives as neutral.

Discussion
The pattern of social media use by adolescents in Porto Alegre, Brazil, is similar to that reported for samples from high income countries. Also, we found that those who reported being constantly online were also more likely to report socializing with their friends offline.