Especially in e-commerce and associated online marketing, web cookies play an essential role as they provide information that is key, for instance, to improving website functionality and customization. With the 2019 ruling of the Court of Justice of the European Union, cookie notices became mandatory in the EU. Companies seek to measure and improve cookie opt-in rates to avoid large data losses relevant for online marketing. We tested in an experiment the most common cookie variants ? the binary-choice cookie notice and the category-choice cookie notice ? for their acceptance rates. The results showed that the former achieved a slightly, but statistically significantly, higher opt-in rate, and the highest opt-in rate was found among users browsing on mobile devices. The decision to accept or reject cookies when presented with a cookie notice is made within seconds and can be influenced by various external factors, which we sought to identify and examine in this study with the use of a survey following the experiment. None of the external influencing factors examined were perceived as influential by more than half of the participants. Simplicity of use, the speed with which the cookie notice is dismissed and time pressure when browsing were the most frequently mentioned external influencing factors. However, all factors examined had some effect on users? attitudes to cookie notices.