Ultraviolet wavelengths represent an interesting and not yet deeply investigated field in blazar physics. In fact, these sources are expected to be signaled at these energies by mean of synchrotron emission from highly relativistic jet electrons, or by thermal emission from an accretion disk according to the unified AGN model. I here report on a recent study on GALEX observations of Fermi detected blazars. Associating the blazars form 2FGL catalog with sources form the GALEX archive I investigated their spectral properties, revealing Fermi blazars among the brightest sources in the UV sky, with bluer GALEX color with respect to the rest of the sources. This places (gamma)-ray blazars on a distinct region of the UV color-magnitude diagram, indicating a tight relation between the physical processes responsible for the emission in these energy bands in the widely entertained external Compton scenario, where jet electrons inverse-Compton scatter thermal radiation from the accretion disk up to (gamma)-ray energies.