The surfaces of inorganic substrates containing hydroxyl groups can be adapted to a variety of physical and chemical requirements by reaction with cyclic azasilanes. The moderately-strained ring structure of cyclic azasilanes containing adjacent Si and N atoms, along with the high oxophilicity of silicon, enables the high reactivity towards available hydroxyl groups on all siliceous surfaces investigated, including amorphous silica and borosilicate glass. The reaction occurs quantitatively at room temperature, requires no catalyst and has no byproducts. This investigation looks specifically at the reaction kinetics by means of DRIFT spectroscopy and quantifies extent of reaction by TGA. The less sterically-hindered the Si–N bond, the faster the reaction occurs. In all cases, the reaction is essentially complete in less than one minute. This study provides the first confirmation that the rate and extent of reaction without catalysis or byproducts of cyclic azasilanes conforms to the Sharpless requirements for “click chemistry” and can be deemed “click chemistry for surfaces.”