Purify is a Proof-of-Concept Android application that can remove advertisements (ads) from any apk (i.e. Android app). It doesn't need root privileges.
This application is just a proof of concept, I wrote it in few hours. The code isn't so tidy and the application can fail. If the application fails, the new purified apk (i.e. without ads) will crash.
Purify takes in input an apk and changes the content of classes.dex. In details, the application looks for well known ads domains (e.g. example.ads.site.com) and replaces the domains with invalid domains. Thus, for example, an application instead to do an http request to example.ads.site.com/banner.php?size=100 will request an invalid url as aaaaaaaaaaaaaaa/banner.php?size=100. For the majority of the apps this should mean that the app will not display any ads. However, some apps can crash, so it doesn't work always.
Purify can edit the classes.dex file inside an apk, it will produce a new purified apk containing the same (old) signature. You can try to install it, however probably you will get an error during the installation asserting that the package is corrupted. A valid apk must be signed, otherwise you can't install it, so you need to use also an apk signer to correctly sign the application. I recommend the open source ZipSigner. Purify requires Android 4.2 or higher.
GPLv3