Know Your App Act This bill requires the National Telecommunications and Information Administration (NTIA) to undertake actions to inform customers about the country of origin of applications (apps) and dangers of certain foreign apps. Specifically, the NTIA must require app stores with more than 20 million U.S. customers to prominently display the country of origin for each app they distribute. In addition, app stores must enable customers to filter out apps that originate from countries of concern. These are countries, identified by the Departments of the Treasury and Commerce, with laws that allow governmental control of content moderation, algorithm design, or user data. App store pages for apps originating from a country of concern must include a disclaimer that warns customers about the potential for a foreign government to control functions of the app. Additionally, app developers must (1) certify to app stores that the information about the app displayed on the app store page, including country of origin and ownership, is correct; and (2) notify app stores about relevant changes in the country of origin or ownership. If a developer fails to provide the certification or update incorrect information, the app store must remove the app. App stores must also establish (1) a reporting mechanism to allow individuals to anonymously report when information about an app is incorrect, and (2) written policies for developers to appeal the removal of an app from the store. The bill provides for enforcement by the Department of Justice.