What is sideloading on Android?

Sideloading means installing an Android app from outside an app store, usually by opening an APK file downloaded from a website, sent in a message or copied from a computer.

Android allows it. On Android 8.0 and later, you allow each source separately: Android’s documentation says users go to the Install unknown apps settings screen to allow installs “from a particular location”, such as a browser or file manager. [1]

Why it matters on Android

There are good reasons to sideload. Developers test their own apps, some apps are only offered on their maker’s website, and some people restore apps from their own backups.

Sideloading also skips an app store’s review. Stalkerware is usually not allowed in app stores, so it is often sideloaded by someone with brief access to the phone. A sideloaded app you do not remember installing is worth a closer look. Many normal apps are installed this way too, so sideloading alone is not evidence of anything.

How Applore uses it

• One signal among several. Needs your review notes whether each app came from an app store, from an APK file, or from another app on the phone. Being sideloaded raises the level only when it comes with other signals, such as a hidden app icon or accessibility access.
• Other stores count as stores. Google Play is not the only store. Applore treats apps from recognised app stores, including some phone makers’ stores and F-Droid, as store installs.
• Your own backups. If you restore an app from an APK you backed up with Applore, Android records it as installed from a file. If Applore flags it and you know you installed it, you can mark it as trusted.

How detection works explains the other signals.