The CFHTLS Wide field survey covers 170 square-degrees spread over 3 uncorrelated areas of the sky. Each patch covers about 7x7 square degrees and is located far from the galactic plane, in order to minimise galactic extinction and bright star contamination. They will all be observed in u,g,r,i and z band, with typical exposure time of 1 hour each.

The main scientific goals are the geometry and large scale structures of the universe, distant quasars and distant clusters of galaxies and the stellar proper motion in the Galaxy. It therefore includes the cosmic shear survey that involves the gravitational lensing (Descart) team. The stellar proper motion follow up is carried out by splitting the r-band data into two sub-exposures: one during the first year of the survey and another one three years after.