What "Install Unknown Apps" Allows and When to Turn It Off

By the Paxio team · October 30, 2026 · 3 min read

When you try to open an APK file, Android may say it blocked the install and offer a switch called "Allow from this source". That switch is the "Install unknown apps" permission, and it is granted one app at a time. It is worth knowing which apps hold it, because an app that can install other apps can install almost anything.

What the permission does

Since Android 8.0, installing apps from outside the store is controlled per app. Each app that wants to start an install, called a source app, needs the user to allow it, and apps can check whether they have that permission with canRequestPackageInstalls().^[1] So when you download an APK in your browser and tap it, it is the browser that gets permission, and only that browser.

For the bigger picture of why installs outside the store are risky, read what sideloading is. This page focuses on the setting itself.

Which apps usually have it

It tends to be requested by apps that handle files or links:

• Web browsers that download APK files
• File managers
• Messaging apps that receive attachments
• Third-party app stores and "app installer" tools
• Cloud-storage apps

Most people need none of them to have it day to day. An app that is allowed to install others, and that you do not recognise, deserves a closer look.

How to check and switch it off

1. Open Settings and search for "Install unknown apps" (on some phones it sits under Apps, Special app access, or Security).
2. Open the list. Each app is shown with Allowed or Not allowed.
3. Set every app to Not allowed unless you are installing a file right now.
4. If an app you do not recognise is allowed, check its other permissions and consider removing it. See spyware signs to look for.

Menu names differ between manufacturers, so the search box is the fastest route.

If you do need to install a file

• Use the developer's own website or a reputable open-source store.
• Look at the app's permissions first. Our APK analyzer shows them without installing anything.
• Allow the permission for just the one app you are using, then turn it off again.
• Keep Play Protect on; it can scan apps on your device and warn about harmful ones.^[2]

What the prompt really means

The prompt reads like a one-time question about a single file, but it is a lasting permission for the source app. Once you tap "Allow from this source", that browser or file manager can start installs again later without asking, until you turn it off. That is why the habit of switching it back off matters more than the first decision.

For parents and shared phones

On a child's phone, an app with this permission can install games that never passed a store's age rating or a parent's approval. Check the list when you set the phone up and again every so often. Talk through why it is off, so a child understands the point instead of just hitting a block when a friend sends an APK.

Analyze an APK →