How to Enable Unknown Sources on Android

On Android 8.0 and later, there is no single "Unknown sources" switch anymore. Instead, you allow one specific app, usually your browser or file manager, to install apps. The fastest way is to open the .apk, tap Settings when Android blocks it, turn on Allow from this source, and go back to install.

This guide covers that quick path, the manual path through Settings, how it looks on Samsung phones, and how to turn the permission off again when you are done.

Why Android blocks apps from unknown sources

Apps from Google Play are reviewed and scanned before they reach your phone. An .apk downloaded from a website, an email or a chat has not gone through that process, so Android blocks it by default to protect your data from malware and spyware.

That protection is useful, but developers and testers often need to install apps that are not on Google Play yet: beta builds, internal tools, or a client preview. In that case you give permission to the app that opens the file, and only to that app.

The quick way: allow it from the install prompt

1. Download the .apk in your browser, for example Chrome, and tap the downloaded file.
2. Android shows a message that your phone is not allowed to install unknown apps from this source. Tap Settings.
3. Turn on Allow from this source.
4. Tap back. The installer opens again. Tap Install.

You only need to do this once per app. The next time you open an .apk from the same browser, the installer opens directly.

The manual way: through Settings

If you prefer to set it up before downloading, the setting lives under the special app access menu. The exact names vary a little by manufacturer and Android version, but on Android 15 with a stock or Pixel style menu it looks like this:

1. Open Settings and tap Apps.
2. Tap Special app access (on some phones it is under an Advanced section or a menu icon).
3. Tap Install unknown apps.
4. Pick the app you will open the .apk with, such as Chrome or Files.
5. Turn on Allow from this source.

If you cannot find it, open Settings and search for "unknown apps".

On Samsung Galaxy phones

Samsung's One UI places the same setting under the security menu on many versions. Open Settings, then Security (or Security and privacy), and tap Install unknown apps.

You will see a list of apps, each marked Not allowed by default. Tap the app you will use to open the .apk.

Turn on Allow from this source. Android reminds you that installing apps from this source may put your phone and data at risk.

Older phones: Android 7.1 and earlier

Before Android 8.0, there was one global switch. Open Settings, then Security (or Lock screen and security on older Samsung phones), and turn on Unknown sources. Very few phones in use today still run these versions.

Google Play Protect: "Install anyway"

Allowing unknown apps is not always the last step. Google Play Protect checks apps that do not come from Google Play, and a test build it has never seen before often gets a warning, for example that the app is unsafe, was blocked, or that a scan is recommended. This is common for new internal builds and does not by itself mean something is wrong with the file.

1. On the Play Protect dialog, tap More details (on some versions the option is already shown).
2. Tap Install anyway. Some versions ask Play Protect to scan the app first; you can let it scan and then install.
3. If the dialog only offers OK or Uninstall, Play Protect has blocked the app on this phone. Ask the developer about it rather than turning Play Protect off.

Only choose Install anyway for a build you expected, from a developer you know. If you were not expecting the file, cancel.

"App not installed": causes and fixes

Android shows "App not installed" (sometimes "App not installed as package conflicts with an existing package" or "package appears to be invalid") for a few different reasons. Check them in this order:

• Signature conflict. The most common cause. A copy of the same app is already on the phone, signed with a different key: the Google Play version, a build from another developer machine, or an older test build. Android only installs an update signed with the same key. Fix: uninstall the copy that is on the phone, then install the new build. Uninstalling removes that app's local data.
• Older version over a newer one. Android does not install a build with a lower version code over a higher one. Uninstall the newer copy first, or ask the developer for a build with a higher version code.
• Not enough storage. The phone needs room for the download and the installed app. Free some space and try again.
• Incomplete download. If the connection dropped, the file may be cut short. Delete the downloaded file and download it again on a stable connection.
• Android too old for the build. Every app sets a minimum Android version. An older phone cannot install it, and only the developer can change that.
• Very old target SDK. Recent Android versions refuse apps built for very old Android versions. The developer has to rebuild with a newer target SDK.
• App Bundle instead of APK. An .aab file cannot be installed on a phone at all. The developer can build an APK from it, or upload the .aab to AppForShare with an account, which turns it into one universal APK testers can install. See How to install an .aab file on an Android phone.

One case to know about builds shared from an .aab on AppForShare: if the APK was signed with the workspace's AppForShare test key, it cannot update the app installed from Google Play. Uninstall the Play version first; the install page says so.

Turn the permission off when you are done

Once your test app is installed, go back to Install unknown apps and turn the permission off for that browser or file manager. The app you installed keeps working. This keeps a random download from installing itself later.

Installing test builds from AppForShare

When a developer shares a build with you through AppForShare, you get a link or QR code. Open it on your phone, tap Install, and allow your browser to install unknown apps the first time. That is the only setting you need on most phones; Play Protect may also ask you to confirm with Install anyway.

The install page also helps when something is in the way. If your Android version is older than the build needs, it says so above the Install button, and its install help list covers unknown apps, Play Protect, "App not installed" and storage, in your browser's language when it is one of the 7 the page supports. It cannot see your phone's settings, so those are steps to check rather than a diagnosis. See Install help for what the page shows.

If you are the developer, see How to use AppForShare to send .apk or .ipa files to your clients.

Frequently asked questions

Where is the Unknown sources setting on Android 15?

There is no global switch on Android 8.0 and later. Go to Settings, Apps, Special app access, Install unknown apps, pick the app that opens the file (such as Chrome) and turn on Allow from this source. Menu names vary by manufacturer.

Do I have to allow unknown sources every time I install an APK?

No. The permission is per app and stays on until you turn it off. After allowing your browser once, later APKs opened from that browser go straight to the installer.

What do I need to install a build shared through AppForShare on Android?

Only the link or QR code. Open it on the phone, tap Install, and allow your browser to install unknown apps the first time.

What does "App not installed" mean on Android?

Most often a signature conflict: a copy of the same app signed with a different key, such as the Google Play version, is already on the phone. Uninstall that copy and install the build again. Other causes are a lower version code than the installed app, too little storage, an incomplete download or an Android version older than the build needs.

Play Protect blocked my test build. What do I do?

Tap More details on the Play Protect dialog, then Install anyway, if you trust the developer who sent the build. If the dialog offers no install option, Play Protect has blocked the app on that phone and you should ask the developer.