Arylazopyrazoles, a novel class of five-membered azo photoswitches, offer quantitative photo-switching and high thermal stability of the Z isomer (half-lives of 10 and similar to 1000 days). The conformation of the Z isomers of these compounds, and also the arylazopyrroles, is highly dependent on the substitution pattern on the heteroarene, allowing a twisted or planar geometry, which in turn has a significant impact on the electronic spectral properties of the compounds.