ImpleMentAll will develop, apply, and evaluate tailored implementation strategies in the context of on-going eHealth implementation initiatives in the EU and beyond. Common mental health disorders account for an alarming proportion of the global burden of disease. Being regarded as an evidence-based psychotherapeutic eHealth intervention, Internet-based Cognitive Behavioural Therapy (iCBT), has the potential to answer to this societal challenge by providing an efficacious and efficient treatment from which more people can benefit. As a result, various iCBT implementation projects are currently conducted across the world. We propose to use this natural laboratory to develop and evaluate a toolkit for tailored implementation strategies that is expected to make implementation trajectories more efficient. The objectives for ImpleMentAll are: 1) To develop a generic Integrated Theory-based Framework for Intervention Tailoring Strategies (the ItFits-toolkit) for data-driven tailored implementation of evidence-based eHealth services. 2) To demonstrate the impact of the ItFits toolkit on the implementation of eHealth for common mental disorders, in 9 European countries, 2 LMIC, and Australia. 3) To disseminate the validated toolkit in various healthcare contexts across Europe. ImpleMentAll is a true multidisciplinary international collaboration that unites key experts in clinical practice, health innovation, clinical research, and implementation science. Combined with it’s unique setup, ImpleMentAll will be able to test if tailoring implementation strategies lead to more efficient implementation. The resulting ItFits-toolkit will enable data driven evaluation of eHealth implementation projects in terms key performance indicators for process, effectiveness, and efficiency outcomes. Its methods, materials, and strategies will provide concrete guidance on tuning implementation interventions to local determinant of practice across a variety of health care systems.