The promise of high safety and stability in solid-type electrolytes has prompted many battery researchers to find candidate inorganic compounds to replace existing liquid/polymer-based electrolytes. In this report, the alkali ion transport in tavorite-type ABTO₄X (A: Li, Na; B-T: Al-P, Mg-S; X: F) is investigated by ab initio calculation, bond valence path approach, and void space analysis in order to explore their viability as solid electrolytes for all-solid state Li/Na ion batteries. Results from nudged elastic band and bond valence pathway methods reveal that the Li analogues are capable of 1D Li ion diffusion (<0.60 eV) characterized by a zigzag pathway along c-axis and passing between BO₄F₂ pairs at each intersite jumps. However, the Na analogues show poor ionic conduction as evidenced by the relatively higher Na migration energy (>0.80 eV) for the same pathway due the larger size of the Na ion and the unchanged critical size along the conduction channel.