We derive the electroweak (EW) collinear splitting functions for the Standard Model (SM), including the massive fermions, gauge bosons and the Higgs boson. Beyond the familiar gauge theory splitting functions, we discuss the emergence of additional ``ultra-collinear'' splitting phenomena and naive violations of the Goldstone-boson Equivalence Theorem. We implement the EW showering and illustrate its importance by calculating a number of physical processes at high energies within and beyond the SM. Novel features in the implementation include a complete accounting of ultra-collinear effects, matching between shower and decay, kinematic back-reaction corrections in multi-stage showers, and mixed-state evolution of neutral bosons ($\gamma/Z/h$) using density-matrices. Because the SU(2) quantum numbers are explicit and observable in common physical processes, subtitles of the Bloch-Nordsieck theorem violation and resummation to the NLL are discussed.