Chloroacetic acid is a stronger acid than acetic acid. This can be explained using

-Cl is an electron withdrawing (ie, $-I$ showing) group. It withdraws electrons when attached to the carboxylic acid and decreases the electron density on the oxygen atom. This will facilitate the release of $\mathrm{H}^{+}$by making $\mathrm{O}-\mathrm{H}$ bond more polar and thus $-\mathrm{Cl}$ increases the acidity of acetic acid when attached at, $\alpha$ position because of -I effect.