Female software developers see their contributions of code accepted more frequently by the open-source software repository GitHub than do men, according to a preprint that attracted much attention last week on social media. But this happened only when the contributor’s gender was not obvious from their GitHub profile page. When gender was made clear, the acceptance rate for women fell to slightly less than that for men, say researchers who analysed data on the activity of more than 1.4 million users of GitHub. Morgan Ernest, an ecologist at the University of Florida in Gainesville, tweeted a link to the paper. But other researchers questioned whether the study, posted at PeerJ PrePrints on 9 February, definitively demonstrates gender bias.