also provides shallower $u,g,r,i,z$ observations in the whole XXL-N area. We used the DR10 data release [@2014ApJS..211...17A].

-   XXL-N has been observed with the WIRcam camera on CFHT in the $K_s$ band (2.2 $\mu$m), see .

-   The UKIRT Infrared Deep Sky Survey (UKIDSS, @2006MNRAS.372.1227D) has two fields (in the J,H,K bands) targeted on the XMM-LSS area, enclosed in XXL-N: the Ultra Deep Survey (UDS), and the Deep Extragalactic Survey (DXS). We used the DR10 data release.

The XXL-S area is covered by the following surveys:

-   The Blanco Cosmology Survey (BCS), using the Mosaic2 imager at the Cerro Tololo Inter-American Observatory (CTIO) 4m Blanco telescope, observed a large southern area, giving full coverage of XXL-S in the $g,r,i,z$ bands [@2009ApJ...698.1221M; @2012ApJ...757...83D].

-   The Dark Energy Camera (DECam, @2015AJ....150..150F), also on the CTIO Blanco telescope, provided deeper $g,r,i,z$ observations of XXL-S [@2015JInst..10C6014D].

The following surveys cover both areas:

-   The Vista Hemisphere Survey (VHS, @2013Msngr.154...35M), using the Visible and Infrared Survey Telescope for Astronomy (VISTA) covered XXL-N and XXL-S in the J,H,K bands. Additional coverage of XXL-N is supplied by the VISTA Kilo-degree Infrared Galaxy Survey (VIKING, @2013Msngr.154...32E) and VISTA Deep Extragalactic Observations Survey (VIDEO, @2013Msngr.154...26J).

-   The Spitzer satellite 