Why is chloride ion a very weak base?

In the context of the Brønsted-Lowry theory, the chloride ion (${\text{Cl}}^{-}$) is considered a very weak base because it is the conjugate base of hydrochloric acid ($\text{HCl}$), which is a strong acid.

According to the principles of acid–base equilibria, there is an inverse relationship between the strength of an acid and its conjugate base. Because $\text{HCl}$ is a strong acid that dissociates completely in aqueous solution, it has a very high tendency to donate a proton. Conversely, its conjugate base, the chloride ion, has an extremely low affinity for protons. In any acid–base reaction, the equilibrium favors the formation of the weaker acid and the weaker base; since $\text{HCl}$ is a much stronger acid than the hydronium ion (${\text{H}}_3{\text{O}}^{+}$), the chloride ion acts as an exceptionally poor proton acceptor in water, rendering it a very weak base.123