Multilingual experience is seen as a cognitive reserve factor that may protect against neurodegeneration. Accurate language use measurement is essential to understand its cognitive and neural effects. Traditional assessments often rely on a single retrospective questionnaire, which may not reflect the dynamic, context-dependent nature of multilingualism. This study introduces complementary tools – Language History Questionnaire (LHQ), Daily Report Form (DR), Online Messages (OM) and In-lab Language Tasks (EXP) – to assess language use across social contexts in native and non-native languages. Correlational, ANOVA and network analyses showed that self-report tools had high internal consistency, while objective and experimental methods varied in sensitivity to context and modality. Consistency across tools was higher for native language use, especially when aggregating data across contexts. In contrast, non-native English assessments were more affected by contextual variability and tool-specific biases. Findings highlight the need for multimodal, context-rich assessments to improve validity and comparability in real-world multilingual research.