For Google, the update to enable the tracking tools won’t be like a normal operating system upgrade. It will instead come through a set of tools called Google Play Services, which lets Android sidestep some fragmentation issues by pushing updates directly, without the approval of device and wireless partners. The company normally uses Google Play Services to update its own apps, like Gmail and Maps, and to push changes like a new app icon. The contact tracing tools will be available for phones running software as old as Android Marshmallow, the version of the operating system released in 2015.

“Given the critical nature of this update, I appreciate Google using the Google Play services rather than relying on users to download the update,” Creative Strategies analyst Carolina Milanesi said.

It likely will be easier for Apple to roll out an iOS update to all of its users at once than it is for Google. Because Apple controls the hardware, software and services on iPhones, it’s able to make sure updates work across its newer devices and roll it out to all devices at once.