Abstract: Methods, systems, and computer programs are presented for determining languages spoken by a user based on analysis of the information and activities of the user. One method includes an operation for extracting values for features, associated with a user of a social network, related to a language. Each feature is a primary or a secondary feature. For each primary feature, a determination is made whether the value of the feature exceeds a threshold. The method further includes operations for determining that the user speaks the language when at least one primary feature exceeds the respective threshold, and when no primary feature exceeds the respective threshold, analyzing values of the primary and secondary features to determine if the user speaks the language. The determination that the user speaks the language is stored in the user profile, and the user interface of the social network is customized based on the language.