When it was active, Casper was popular for features that the official app lacked: Download media directly to your gallery.
Go to Settings > Security and toggle on "Unknown Sources."
The original developer, Liam Cottle, ceased development years ago due to legal threats from Snapchat.
Tap the APK and follow the on-screen prompts. Log In: Use your credentials (at your own risk). Top Modern Alternatives
Currently, Casper (including "Plus" versions) is for the following reasons:
Use built-in system tools for saving content (though notifications may still trigger).
Find the downloaded file in your Downloads folder using a file manager.