This study investigated Alay language on social media made by teenagers. This research applied documentary method. The techniques used in collecting data were: The researcher observed and collected Alay language vocabularies that used in social media by screenshot them afterword the researcher copied the data and gave a code. The techniques of analysis were: the researcher Collected and selected the data which can be categorized as Alay language and Classified the data based on the forms of Alay language. This research was focus on the analysis of the Alay vocabulary in social media made by teenagers. The researcher obtained 27 Alay vocabularies used by teenagers in social media. Structures vocabulary and sound changes at the Alay language among teenager in a Facebook group namely; JUAL BELI ONLINE LOMBOK is: The Addition of Phoneme, Phoneme Omission, Abbreviation, Using other terms, Replacement Letter, Capital and Lower Case Letter, Combination of Letter and Number, and Letter, Abbreviation, Symbol, Number.