AdAway

AdAway blocks advertising on Android at the name-resolution level. In its original mode it needs root: downloaded host lists are merged into the system hosts file, so requests to ad and tracker domains resolve to a dead address for every application on the device at once. A second mode works without root by running a local VPN service that filters DNS queries on the phone itself, without routing traffic to any outside server.

The host sources are a list of URLs you can extend, and each source is enabled or disabled on its own. On top of them you keep personal allowed, blocked and redirected entries, which is how you undo a list that breaks a site or an app you need. In the root-free mode the application can show which domains are being requested, which makes it easier to work out what to block or let through.

The method has a boundary worth knowing before installing it. Filtering happens by domain name, so advertising delivered from the same host as the content around it is not affected, and blocked slots may leave blank space in a page or an app rather than disappearing.