What Is MicroG / GmsCore?
MicroG is an open source reimplementation of the Google Play Services APIs, distributed as GmsCore in the ReVanced ecosystem. A sideloaded app uses it to sign into a Google account, receive notifications and sync data, with no root access required.
How MicroG works
Android apps reach Google services through Play Services, a proprietary system app that only answers requests from apps Google recognizes. A patched YouTube is signed with a key generated on your own device, so Play Services will not serve it. MicroG provides the same programming interfaces under its own package, and the patched app is built to call it instead. When you sign in, GmsCore runs Google's own web login flow, keeps the resulting account token, and hands it over whenever the app asks for one.
In the Vanced context
Vanced MicroG was a separate build that handled Google login for YouTube Vanced. It has received no maintenance since the project ended in March 2022, and Google has changed its authentication flow repeatedly since. Login failures on leftover Vanced installs are now routine, and in most cases there is no repair available: the build that would fix them was never released and is not coming.
In the ReVanced context
GmsCore is the maintained successor and the one to install for a non-root ReVanced setup. Take it from the official ReVanced GitHub repository, install it before the patched app, and keep it current, because sign-in is the part of the setup most affected by changes on Google's side. Pair it with the YouTube version that Manager recommends rather than an arbitrary build.
What it looks like when it breaks
A working setup sends you to an account chooser and returns you to a signed in app. A broken one usually loops: you sign in, the app looks signed out again, and nothing explains why. The two most common causes are a GmsCore build that is out of date and a power manager suspending GmsCore in the background, which breaks the token refresh a while after login appeared to succeed.
Common misconceptions
MicroG is not made by Google and is not a way around paying for anything. It does not bypass account security, and you still sign in with your own credentials through Google's own page. It is also not required for playback: a non-root ReVanced install plays video perfectly well signed out, it simply has no access to your subscriptions, history or playlists. Vanced MicroG and GmsCore are not interchangeable either, and installing both at once causes the failure people usually install the second one to fix.
Before you install
Always download patchers, GmsCore, and APK bases from official project pages or trusted mirrors listed in our safety guides. Mismatched versions are the most common cause of playback and login failures after setup.