Inclusion Criteria:  Literate Brazilian portuguese speakers. Insomnia symptoms (as measured by ISI). An Android-based smartphone or tablet with access to the Internet.  Exclusion Criteria:  Previous experience with CBTi. Use of sleeping pills or any other treatment for insomnia for two or more days a week in the last three months. Presence of self-reported co-morbidities (hypertension, hyper/hypothyroidism, asthma, bronquitis or other respiratory diseases, rhinitis, epilepsy and other neurological diseases, any psychiatric disease other than depression and anxiety, diabetes) or sleep disoders other than insomnia.