Android pop-up ads are usually caused by adware apps disguised as PDF readers or media players, installed by tapping misleading prompts on websites or links in WhatsApp chats. Remove them by reviewing all installed apps in the Google Play Store under Manage Apps, uninstalling anything unfamiliar, and checking Settings under Apps and Special App Access for hidden entries. Prevent reinfection by only installing apps you chose yourself directly from the Play Store and keeping Google Play Protect active.
