X-ray polarization of Blazars

Polarization carries information about the geometry and structure of the magnetic field in blazars jets, as seen by the emitting particles. So far such studies were possible only from radio to optical frequencies. With the advent of IXPE, it is now possible to measure linear polarization in the X-ray band for several type of blazars. In high-energy-peaked blazars the X-ray band is fully dominated by the synchrotron emission of freshly accelerated electrons. Since X-ray electrons cool much faster then optical electrons, IXPE is probing the structure of the magnetic field on smaller scales and closer to the acceleration sites. Here I give an overview of the first IXPE observations of blazars, discussing the results in the context of their SED.