The Xcat-DB contains all of the sources contained in the XMM archive sources catalog extracted from more than 200 catalogs hosted for the most part at CDS. It also offers direct access to XMM data (images, lists of sources at camera level, light curves and spectra) as well as visualization and comparison tools (online spectral adjustment, access to the Virtual Observatory). It is possible to select X-ray sources on the basis of their positional correlation (or to note the absence of correlation) with entries extracted from astronomical archive catalogs. The database accepts complex queries that can be easily edited. Its interface is equipped with interoperability capabilities allowing at any time to consult external databases in relation with the locally selected data.