With the advance of online social networks, the screening of applicants during hiring can extend beyond the usual application material. Although browsing the online pro…le of an applicant raises ethical issues, this practice potentially improves the job matching, at virtually no cost to the employer. In this paper, we investigate the use of online social networks as a reliable source of information for recruiters on applicants in the French job market.We set up a …eld experiment using real accountant job o¤ers in the greater Paris area. We adjust the content of Facebook accounts to manipulate the perceived origins of applicants (hometown and language spoken) and analyze the impact on the number of callbacks received from employers. The signal we manipulate to distinguish applicants is available only within the online pro…le, not the application material. During a 12 month period from March 2012 to March 2013, we submitted more than 800 applications. The test applicant received a third fewer callbacks compared to the control applicant, a signi…cant di¤erence. Our results suggest that online pro…les are used indeed to screen applicants, and that this occurs early in the hiring process.During the course of the experiment, a change to the standard Facebook layout sent a part of our signal, namely the language spoken by the applicants, into a sub-tab not directly visible from the front page. This exogenous change (clicking on a tab is now required to access the information) allowed us to measure the recruiter's depth of search. In subsequent months, the gap between the two applicant types shrank and virtually disappeared. This suggests that screening is super…cial, illustrating the existence of employer search costs for browsing an entire pro…le.