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In the article, the priority importance of the proactive monolithic decision-making mechanism implementing for the simultaneous development of offline and digital business of retailers is reasonably proved. The analytical and synthetic tools for optimizing the retailers’ online activity as a component of the mechanism are proposed. Implementation of the tools will play a key role in the modern realities of market trends changes and the external environment bifurcations. The gradation-conversion shift matrix is developed and tested. It determines the set of relevant events in the discrete and continuum stages of the retailers’ digital business development. The system of relevant measures for increasing the efficiency of online retailers functioning through step-by-step implementation is developed and interpreted taking into account the stages of the digital business development.