Injuries and deaths from firearms are increasingly recognized as a public health crisis in the U.S. Studies investigating whether background check requirements reduce firearm-related homicide and suicide have been inconclusive, though some studies suggest these requirements may be effective at reducing firearm deaths. Currently, federal regulations require that firearm dealers with a federal firearms license conduct a background check before sales. However, although some states require private sellers to conduct a background check, federal regulations do not require private sellers to conduct background checks. In the last decade, online firearms marketplaces for private sellers have emerged, potentially allowing buyers to circumvent background checks by purchasing firearms through a private sale. One such popular website is Armslist.com. The objective of this study is to identify the number and percentage of firearm listings in which sellers on Armslist.com indicate they are seeking evidence of some form of a background check from a buyer before the purchase of a firearm.