The RAPID2021 workshop focused on a specific and contemporary research topic: detector technology and electronics for nuclear and particle physics experiments as well as applications. In the RAPID2021, we had invited lectures, overview talks and contributed presentations by the scientists and young researchers from all around the world. In this workshop the papers presented are on the new developments at different experiments (ALICE, CMS, ATLAS) at CERN, new micro-pattern gas detectors development by RD51 collaboration at CERN, development of silicon pixel sensors at CERN, detectors for FAIR facilities in Germany, low energy experiments at different facilities, new detector ideas for nuclear and particle physics experiments, developments in electronics to overcome the challenges for the future LHC experiments, and application of the detectors on medical imaging. The proceedings of the workshop are quite helpful to document the new results, technologies, and developments by different groups and well known international laboratories like CERN, GSI, and Brookhaven National Laboratory. The publication of the scientists and young researchers will definitely be the new references for future studies on the same direction.