Abstract This paper investigates the relationship between competition intensity and the security level provided by software vendors, in particular when the software is free of charge to users. We examine the case of web browsers, a key component of internet security where vendors compete on quality and generate revenue through advertising. Using a pooled cross-sectional dataset on web browser security patch releases from 2009 to 2018, we analyze how competition affects the promptness of these releases. Our findings reveal that higher market concentration can enhance a vendor’s responsiveness in addressing vulnerabilities, though this positive effect weakens when a vendor becomes excessively dominant.