Like many other Android phones, Xiaomi and Redmi mobile phones also come with their own app store, the MIUI Market. Sometimes however you may want to download Android apps, APK files from third party Android market, like Google Play, or install APK files received from other Android phones. When you downloaded some APK file on Xiaomi device or receive apps from other phones and want to install these apps, you may find the installation being blocked. This is the default security setting on Xiaomi or Redmi phone to block the installation of apps from unknown sources. You can turn this feature off in Settings, just like how you can install Apps from unknown sources on Android phones. If you want to install any app or APK on Xiaomi or Redmi mobile phone, you can follow below instructions to allow installation of apps from unknown sources on Xiaomi Redmi phones.
Note that I am using MIUI 8 in this demo. If you use other MIUI version, you may find a little difference.
How to allow installation of apps from unknown sources on Xiaomi Redmi phones?
From your Xiaomi phone home screen, tap to open Settings. Scroll down to the SYSTEM & DEVICE section, choose Additional settings >> Privacy >> Unknown sources. Touch the Unknown sources toggle to turn it on to allow installation of apps, apk files from unknown sources.
After that go to find the downloaded apk file using the File Explorer and manually install the app on your Xiaomi or Redmi phone from there.
How to allow installation of apps from unknown sources temporarily on Xiaomi Redmi phones?
If you do not want to change the security settings on your Xiaomi or Redmi phone, you can also choose to temporarily grant the permission for current app installation from unknown sources. Tap on the APK file you want to install from the Explorer on Xiaomi or Redmi phone, you will see the warning message as below.
Your phone is set to block the installation of apps from unknown sources. You can turn this feature off in Settings.
At the bottom of this dialogue you have the option to Allow once. This means you can allow the installation of current app temporarily, it will not affect future app installations.
Now you know how to allow installation of apps from third party APK markets or websites on Xiaomi Redmi phones. However you will need to make sure the APK files downloaded from third party sites or markets are safe before you install them on the phone.