Hydrolyzes terminal GlcNAc residues from terminally unbranched N-glycans and from chitobiose. Hydrolyzes beta-1,6-linked N-acetylglucosamine and beta-1,4-linked N-acetylgalactosamine from pNP-alpha-GalNAc[beta1,3Gal]beta1,6GlcNAc and pNP-beta-GlcNAc-beta1,4-GalNAc substrates, respectively, as well as beta-1,2-linked N-acetylglucosamine units from the non-reducing end of N-glycans. Hydrolyzes GlcNAc residues linked to alpha1,3- or alpha1,6-mannose branch, but has low activity on substrates with more than one GlcNAc residue on one of the mannose branches. Releases terminal GlcNAc moieties from the N-glycopeptide Gly-Glu-Asn-(GlcNAc2Man3GlcNAc2)-Arg with high efficiency. Has moderate hydrolytic activity on the chitobiose moiety of N-glycopeptide substrate Gly-Glu-Asn-(GlcNAc2)-Arg. Does not hydrolyze GlcNAc residues from N-glycan structures bearing a bisecting GlcNAc moiety (beta1,4-linked GlcNAc to the beta1,4-linked core mannose) (PubMed:29304441). Potentially capable of cleaving the specific glycoside linkages in the process of mucin degradation in human intestinal tract (Probable). Hydrolyzes synthetic substrate pNP-beta-GlcNAc with high activity and pNP-beta-GalNAc to a lesser extent (PubMed:29304441, PubMed:30846208). Does not hydrolyze pNP-beta-glucose, pNP-beta-galactose, pNP-alpha-glucose, pNP-alpha-galactose, pNP-alpha-GlcNAc or pNP-alpha-fucose (PubMed:29304441). Hydrolysis of terminal non-reducing N-acetyl-D-hexosamine residues in N-acetyl-beta-D-hexosaminides. Significantly inhibited by the addition of sodium dodecyl sulfate (SDS), but not by EDTA, urea, 2-mercaptoethanol or Triton X-100. Strongly inhibited by Cu2(+) ions, in case of which the activity is decreased by 70%. No significant inhibition with Al(3+), Fe(3+), Ca(2+), Cd(2+), Mg(2+), Mn(2+), Ni(2+) and Zn(2+) ions. Strongly inhibited by PugNAc (O-(2-acetamido-2-deoxy-D-glucopyranosylideneamino) N-phenylcarbamate) in the sub-micromolar concentration range. PugNAc at a concentration of 0.5 mM decreases the activity by 50% and the addition of 1 mM PugNAc fully inhibits the enzyme. No significant reduction in the activity by alkylation using N-ethylmaleimide or 2-iodoacetamide. kcat is 1.01 sec(-1) and kcat/KM is 34.34 mM(-1)sec(-1) with pNP-beta-GlcNAc as substrate. Optimum pH is 5.0. The activity drops sharply below pH 4.5 and above pH 5.5. Optimum temperature is 37 degrees Celsius. Retains more than 90% of activity after 96 hours of incubation at 37 degrees Celsius and after 12 hours of incubation at 42 degrees Celsius. Belongs to the glycosyl hydrolase 20 family.