As many people are now aware, your online activity is being tracked. As you move between different connected devices, from your cell phone to your laptop to your smart TV, companies are watching, recording, and analyzing your viewing, shopping, and behavioral data. Previously, your activity on each of these devices was isolated within the device. However, as we increasingly change between devices in the course of our day, advertising companies are tracking your online activity between devices in order to create a detailed profile of you through the use of cross-device tracking. The amount and granularity of data that your online activities create is only growing as more devices are connected to the Internet and as our devices become more mobile. Due to the amount of geolocation data that your phone, laptop, and smart TV produce, companies not only know what you are doing online, but where you are. The FTC, understanding the privacy implications of cross-device tracking, will be holding a workshop on November 16, 2015 on cross-device tracking; CDT submitted these comments to the Federal Trade Commission (FTC) last Friday in anticipation of this workshop.