What is sideloading? It's a term you see a lot thrown around while talking about Android applications, and it's simple to explain. It means installing applications without using the official Android Market. What's less simple is how it's done and why you would do it. That's where this post comes in. Let's explain it, shall we?
How to do it is easy enough, so let's start there. In the Application settings on your Android phone, you'll find a check box to "Allow installation of non-Market applications." When it's checked, you can sideload. You'll also see a pop-up warning when you check this box letting you know that your phone is now more vulnerable to attacks from applications, and that you accept all the responsibility that comes with doing this. It makes sense -- you can't hold Google responsible for applications you didn't download through their service using their security methods.
Sideloading apps is easy to do as well. You download them to your phone, then use a file manager application to find them and "click" their entry. You'll invoke the app installer program, and it will install your app just as if it had came from the trusted Android Market. It won't be associated with your Android Market account, but it shows in your app drawer just like all the rest. It didn't used to be this easy for everyone. Under the guise of security, AT&T used to block users from sideloading by removing the Unknown sources field in the device settings. Whenever you tried to manually install an app, it would be blocked because it wasn't allowed. This could be circumvented by using adb from the SDK or by using a program like the Sideload Wonder Machine. Luckily, those days are past us and AT&T has re-evaluated their position, and now allows the installation of non-Market apps.
Why would you want to sideload. There are several reasons, one being that Google has allowed carriers to block certain applications based on the model and network your device is running on. We've seen carriers block apps that permit tethering without paying the extra associated fees, and some carriers have exclusives for certain apps and they aren't available for the others. That's a whole other mess that we'll tackle in another post -- just know that it happens. There are other reasons to need to sideload apps, too. Want to use a different appstore like the one from Amazon? You'll need to enable sideloading. The same goes for beta testing apps for developers, or even coding your own apps and testing them on your phone. There are a lot of legitimate reasons for sideloading. Of course, there's always the piracy aspect. If you want to steal from hard working developers you'll need to enable sideloading. You also suck. Sideload, but don't steal from developers.