Google is a pretty ubiquitous name in the Android space. Not only does the company own and maintain the Android Open Source Project itself, but it's also in charge of the largest distribution platform on Android: the Google Play Store and the underlying Google Mobile Services (GMS) suite. GMS is the important part here. Firebase, Google's cross-platform toolkit for things like analytics and crash detection, uses GMS to provide a lot of its functionality.

That's all well and good if your target devices come with Google apps preinstalled, but what if they don't? What if a user has unlocked their bootloader and flashed a Google-free ROM? What if someone's using a Huawei device, or they've imported a phone from China? Will the Firebase-dependent parts of your app just not work?

Thankfully, if you're trying to implement Firebase into your app, you don't need to guess which SDKs will work on Google-free devices and which won't. Google has helpfully released a list of all its current Firebase SDKs, and whether or not they depend on GMS. You can use this to tell at-a-glance which SDKs you can safely implement and which you may have to supplement or avoid.

Here's a table listing the Firebase SDKs and whether or not they have GMS dependencies:

A surprising number of Firebase SDKs actually work fine without GMS being installed. Even the Authentication SDK can be used without GMS with the right implementation.

Keep in mind that this list is only accurate as of the publication of this article, which is on September 6th. It's possible it will change in the future as SDKs are added, updated, or removed from Firebase. For up-to-date information, as well as a workaround for using Firebase Authentication without GMS, check out Google's page.