The ParticipaTIC Erasmus+ project led by the EHESP School of Public Health in partnership with disability organizations and associations from France, Belgium, Switzerland, and Romania has co-designed an accessible digital platform. In line with the 2010-2020 European strategy and the United Nations Convention on the rights of disabled persons we aim to strengthen the competences of the leaders of disabled persons’ organizations to defend the rights of disabled people, and to develop participation. ParticipaTIC offers 4 modules on ‘What is disability?’, ‘Competencies for disability organization leaders’, ‘the United Nations Convention’ and ‘How to carry out a local accessibility analysis’. Different contrasts, font size, speech synthesis, captioned videos and content summaries in ‘Easy to read and understand’ French are available together with a cloned platform in Romanian and English. Two guides have also been produced on 1) on-line accessibility and 2) co-constructing an on-line accessible platform. Beyond the deliverables, adapting on-line instruction to the different capacities of people with disabilities raises many issues. New competencies for accessible design are needed. Tradeoffs between content, pedagogical style and accessibility seem inevitable. On-line activities need adaptations but these may be complex and costly. Taken-for-granted assumptions about what is attractive, and well-designed are called into question when designing for people with visual, auditory, and intellectual impairments. Lessons from ParticipaTIC are remarkably similar to those of participatory thinking design: advance in small steps, evaluating successive design phases with people with disabilities for fitness of purpose. Ultimately trainers need to redesign themselves to take into account unsuspected worlds, those of our fellow citizens with different capacities. Important lessons beyond the world of on-line instruction for the building of a truly inclusive society have emerged.