A novel flexible electrochemical microreactor has been developed. Flexibility is reached by a modular design, suitability for a broad process parameter range including high pressure operation, and accessibility of production scale. Selected reactor aspects have been validated by applying the reactor to three different electrosyntheses: synthesis of tailor-made mixtures of paraffins by Kolbe electrolysis, cation flow method, and synthesis of peroxodicarbonate. High conversion rates, yields, selectivities, and Faraday efficiency levels have been observed, showing precise process control.