Instead, we started our research by considering all the DOCSIS 3.0 and DOCSIS 3.1 modems that work on the nation’s biggest ISPs: Astound (RCN), Charter, Cox, Mediacom, Optimum, Sparklight, Spectrum, WOW, and Xfinity. We then narrowed the field to modems compatible with the most popular plans on those ISPs. (Astound, Optimum, and WOW don’t publish a list of approved modems, though, and with few exceptions they wouldn’t verify whether any of our picks would work with their services. If you have service with one of these providers, contact customer support to confirm whether your modem will work with the network.)