The Assessment of Language in Adults using Self-reported Skills (ALASS) is an online tool aimed at providing a rapid indication of language-related skills at two levels: basic performance and social use. In Study 1, we have developed and validated a new tool with two objective measures: a lexical decision test and a grammaticality judgement test, completed online by 280 participants (204 women, 69 men, 7 undisclosed, age: M = 24.4 years; SD = 11.1). Results show that ALASS is a good predictor of the outcomes for reaction times in the objective measures. In study 2, we have run further analyses with a subset of 209 adults (157 women, 47 men, 5 undisclosed; age: M = 20.9 years; SD = 5.8) to validate the social implications of ALASS with another online study, also showing a considerable explanatory power in this case, and strengthening the divergent nature of language when it is used with a social purpose against a more cognitive function (i.e. literacy and language production and comprehension). Considering its explanatory power for lexical performance, we believe that the scale has a potential applicability in the assessment of adults that could have missed a diagnosis of Developmental Language Disorder during childhood.