Amazon's Fire TV devices run a heavily-modified version of Android, which means you can install some Android applications on it. While the built-in Amazon Appstore does have a wide selection of apps and games, you can still install software not available through the official store (like the Kodi Media Center) if you have the APK file.
However, there are a few caveats to the process. First, Fire TV devices aren't fully compatible with all Android apps — many games and apps are designed for a touchscreen, not a physical remote. Also, the Fire TV doesn't support Google Play Services, which some software uses for notifications, licenses, and other functionality. Finally, some Fire TV models run fairly old versions of Android (even the latest Fire TV Stick uses Android 7.1, released from 2016), so applications that require newer OS features may not work properly.
Still, you probably won't know if an app works until you try it, so we've put together this guide on how to sideload any Android app (in APK format) onto your Fire TV.
Install APKs from an Android phone or tablet
There are a few mobile apps that can copy applications to a Fire TV device, but the best option is Apps2Fire. It's available from the Play Store, and can copy APK files or your phone's own applications to your Fire TV.
Before you can do anything with Apps2Fire, you have to enable ADB Debugging on your Fire TV, so the app can install applications. Turn on your Fire TV, go to the Settings menu, and select 'My Fire TV.' You should see a menu for Developer options — open it and set 'ADB debugging' to ON. The below video should help you know where to look.
Once you open Apps2Fire for the first time, head to the 'Setup' tab to select your Fire TV from the network. If the app can't find your Fire TV device, make sure it's powered on. If it still can't locate the IP address, go to the Fire TV's Settings page, press 'My Fire TV,' then select 'About.' Finally, scroll down to 'Network' — the IP address will be displayed on the right side.
After the setup process is complete, you can either select an app installed on your phone to copy to your Fire TV, or pick an APK from your device's local files. To select a downloaded APK file, press the Upload button at the top-right, then navigate to the /storage/emulated/0/Download directory.
The installation process can take a while, depending on which Fire TV model you have and how fast your Wi-Fi is, but in the end you should see your installed app in the "Your apps & channels" row on the home screen.
Install APKs from your PC with ADB
Like all Android devices, you can use the Android Debug Bridge (or ADB, for short) to transfer APKs to a Fire TV device. However, since it's a bit difficult to use ADB over a USB connection with Fire devices, it's best to do it over a Wi-Fi connection.
The first step is to install ADB on your computer. It's officially available as part of the Android Studio SDK, but that can be daunting to set up if you're not a programmer, so it's best to use a third-party installation tool. If you're on Windows, 15 Seconds ADB Installer is a popular option that has always worked well for me. If you're using macOS, Linux, or Chrome OS, give Nexus Tools a shot (full disclosure: I made it).
After you install ADB, try typing the command "adb --help" (without the quotes) in your Terminal/Command Line application and press Enter. You should see something like the below screenshot. If you get an error or other message, try closing and re-opening the Terminal/CMD window and try again.
Now it's time to connect to your Fire TV. Turn on your Fire TV, go to the Settings menu, and select 'My Fire TV.' You should see a menu for Developer options — open it and set 'ADB debugging' to ON. The below video should help you know where to look.
Once that's done, you have to find the IP address of your Fire TV. On the main Settings page, press 'My Fire TV,' then select 'About.' Finally, scroll down to 'Network' — the IP address will be displayed on the right side. Make a note of it.
Now it's time to connect ADB on your PC to your Fire TV. Go back to your PC and run "adb connect" (without the quotes), followed by the IP address of your Fire TV. You should see a message that ADB successfully connected — you can also run "adb devices" to verify.
Finally, you can now install whatever APK files you want. If you don't already have an app you want to try out, we'll use the Kodi Media Player as an example, since it's not available from the Amazon Appstore. Go download the latest version from APKMirror, and once the APK file is fully downloaded, we can try sideloading it.
Back in the Terminal/Command Line, type in "adb install" (without quotes), then a space, then drag the file you downloaded into the app window. It should paste the full path to the file. Then press Enter and watch the magic.
If you got a "success" message, the app should now be visible on your Fire TV. Go to the home screen, and scroll through the "Your apps & channels" row until you see the app. The application might have a blank header image, but the name should still be visible when selected.
If you want to sideload more APKs in the future, all you have to do is run the ADB connect command again on your PC, then run the install command for each APK. Super easy.