Sideloading APKs on a Fire TV Stick unlocks apps Amazon doesn't list — but done carelessly, it's also how malware gets in. Here's the safe way to do it.
1. Enable installs from unknown sources — narrowly
Go to Settings > My Fire TV > Developer Options > Install Unknown Apps, and turn it ON only for the Downloader app. Never enable it globally.
2. Install the Downloader app
Get "Downloader" by AFTVnews from the Amazon Appstore. It's the standard, trusted tool for sideloading.
3. Download only from trusted sources
This is where most people go wrong. Shady APK sites bundle adware into popular apps. Stick to sources that use HTTPS, show a clear version history with update dates, and whose file sizes match the official release.
4. Verify before installing
Check the file size, scan the file with an online antivirus, and review app permissions after install — a video app asking for contacts or SMS access is a red flag.
5. Install, then clean up
Open the APK through Downloader's file browser, install it, then delete the APK file to free up space.
A detailed walkthrough with screenshots: How to Download & Install MovieBox APK on Any Device
