Think twice before you install an Android Package Kit (APK) file whose source code is unknown. Various cybersecurity companies find malicious applications that can hide from users, retrieve stored data, download additional malicious apps, and display advertisements. Have you ever heard of Xhelper and Ransomware?
The things above are not a problem if you want to test an Android application that you developed yourself.
Enable Install Unknown Apps on Samsung OneUI Android Oreo 8 & Pie 9
- Open the Settings menu → Apps.
- Tap the three-dots icon (upper-right).
- Select Special Access.
- Tap the Install unknown apps.
- Select the application source then tap Allow from this source to turn it on or off.
Enable Install Unknown Apps on Samsung Experience Android Nougat 7 & Lower
- Open the Settings menu.
- Tap Lock Screen and Security. If it's not available, tap Security.
- Tap the Unknown Sources switch to turn on or off.
- To continue, review prompt then tap OK.