Currently, social media has become an effective medium for communicating and sharing digital content with anyone. Most social media's active users are Gen Z’s people. Indonesians Gen Z usually communicate with others on social media by switching their code to another and using slang. Switchover from Bahasa Indonesia to other dialects or to English and use slang have been dominated on social media. This study observes the reasons that underlying Indonesians Gen Z perform code-switching and use slang also the advantages and disadvantages that will arise. The research method used is descriptive qualitative research. Data were collected from journals, reports, or books that had written by other researchers and analyzed by content and discourse analysis. This research found that there are some reasons also three advantages and a disadvantage of doing code switching and using slang on communication in social media.