IntroductionAt least 85% of unplanned admissions to critical care wards for children and young people (CYP) are associated with clinical deterioration. CYP and their families play an integral role in the recognition of deterioration. The Paediatric Critical Care Outreach Team (PCCOT) supports the reduction of avoidable harm through earlier recognition and treatment of the deteriorating child, acting as a welcome conduit between the multiprofessional teams, helping ensure that CYP gets the right care, at the right time and in the right place. This positions PCCOT well to respond to families who call for help as part of family activation.AimThis protocol details the methods and process of developing a family activation rapid response online application.MethodsThis is a single-centre, sequential, multiple methods study design. Firstly, a systematic review of the international literature on rapid response interventions in paediatric family activation was conducted. Findings from the review aimed to inform the content for next stages; interviews/ focus groups and experience-based co-design (EBCD) workshops. Participants: parents / caregivers whose children have been discharged or admitted to an acute care hospital and healthcare professionals who care for paediatric patients (CYP). During interviews and workshops participants’ opinion, views and input will be sort on designing a family activation rapid response online-app, detailing content, aesthetics, broad functionality and multi-lingual aspects. Further areas of discussions include; who will use the app, access, appropriate language and terminology for use.A suitable app development company will be identified and will be part of the stakeholders present at workshops. Data obtained will be used to develop a multi-lingual paediatric family activation rapid response web based application prototype.Ethics and disseminationFull ethical approval was received from the Wales Research Ethics Committee 2.Cardiff; REC reference: 22/WA/0174. The findings will be made available to all stakeholders.