Anhydrous A𝑙C𝑙₃ is covalent while A𝑙F₃ is ionic. This is justified by

According to Fajan’s rules, if the cation size is large and anion size is small, then the compound will have more ionic. Contrary if the cation size is small and the anion size is large, then compound should be a covalent.

In anhydrous ${\mathrm{AlCl}}_3,$ , the anion ${\mathrm{Cl}}^{-}$has large size hence it can polarize easily and forms covalent bond with ${\mathrm{Al}}^{+3}$. But in the case of ${\mathrm{AlF}}_3$ the anion F− size is small. Therefore, F− ion reacts with ${\mathrm{Al}}^{+3}$ to form ionic bond.