For in vitro transcribed (IVT) mRNA-based immunotherapies such as CAR-T and cancer vaccines, the design of key mRNA components, including the coding sequence, untranslated regions (UTRs), and poly(A) tail, is crucial for success. Optimizing UTRs and poly(A) tails often requires specialized expertise and time. However, coding sequence optimization is easily accessible using VectorBuilder’s free, powerful online biotool. In this hands-on workshop, we demonstrate how to refine coding sequences in just a few clicks, streamlining design and accelerating development for researchers at any level.