PeerPlay
PeerPlay runs on Firebase: the app's data lives in Firestore, the server logic runs in Cloud Functions, and this blog is served from Firebase Hosting. So when developers ask whether Firebase App Distribution can replace Google Play closed testing, I understand the appeal. It is fast, it is free, and it is already in the console you have open.
The short answer is no, not for the 12 testers, 14 days rule. The longer answer is that the two tools do different jobs, and many developers end up using both. Here is how they compare, and how to avoid the one trap that comes with mixing them.
What each tool is for
Firebase App Distribution sends a build of your app directly to people you invite. You upload an APK or app bundle, add testers by email or share an invite link, and they install it, usually through Firebase's App Tester app. There is no store listing and no Play review, so a build can reach testers within minutes of uploading.
Google Play closed testing runs through Play Console. You upload a build to a closed track, add testers by email list or Google Group, and they opt in through your link and install the app from the Play Store, exactly like a real user would. Builds usually go through Google's review before testers get them.
Only one of them counts toward the 12
For newer personal developer accounts, Google asks for at least 12 testers opted in to a closed test for 14 days in a row before you can apply for production. That count lives in Play Console, on your closed testing track. Google has no way to see who installed your app through Firebase App Distribution, so those testers don't count, however many there are and however often they open the app.
As far as Google documents it, internal testing doesn't count either. It has to be a closed track. If your goal is production access, your 12 testers need to be opted in there.
Where App Distribution still wins
Speed. If you want a designer, a friend or a single bug reporter to try a fix today, App Distribution gets it to them before a Play review would even start. It is a good fit for the days before your closed test, when the app still changes every few hours and you only need two or three people looking at it.
Less setup for the tester. They don't need to be on a tester list in Play Console or find your app through an opt-in page. They follow an invite and install. For a quick look, that is much less friction.
Separate audience. You can keep a small inner circle on App Distribution for rough builds while your closed testers on Play only get the stable ones. That keeps your 12 testers away from the build that crashes on launch.
The trap: two builds, one phone
If one person is in both groups, watch the signing key. A build from App Distribution is usually signed with your own key. A build from the Play Store is signed by Google if you use Play App Signing. Android won't install one over the other when the signatures differ, so the tester has to uninstall first.
That uninstall is where closed tests get hurt. The tester removes your Play build to try the App Distribution one, forgets to reinstall it, and stops opening the app from the Play Store for the rest of the test. If you use both tools, keep your 12 closed testers on the Play build only, and use different people, or a separate debug package name, for App Distribution.
A simple way to use both
Use App Distribution while the app is still rough, for fast builds to a handful of people. Once it is stable enough that a stranger could use it, upload it to a closed track and start recruiting for the 14 days. After that, ship updates to the closed track as you normally would. Updating mid-test does not reset the count, as long as your testers stay opted in.
And if the hard part is not the tool but finding 12 people who stay for 14 days, that is the problem PeerPlay is built for: developers test each other's apps from the Play Store, through each app's real closed track.
FAQ
Does Firebase App Distribution count toward Google Play's 12 testers?
No. The requirement is counted on your closed testing track in Play Console. Testers who install through Firebase App Distribution aren't visible there.
Can I use Firebase App Distribution and closed testing at the same time?
Yes. Many developers use App Distribution for quick builds to a few people and a closed track for the 14-day test. Keep the two groups separate.
Why can't a tester install my Play build after an App Distribution build?
The two builds are usually signed with different keys, so Android requires uninstalling one before installing the other.
Does internal testing count toward the 14 days?
As far as Google documents it, no. The requirement is about testers opted in to a closed testing track.