From 2023, Fitbit users will start migrating over to a Google account, rather than signing in with their current Fitbit accounts. 

To begin with it won't be mandatory. Existing users will be able to continue signing in using their Fitbit account; but by 2025 all users will be migrated over, and have to sign in with a Google account. 

There will be an option to migrate your fitness tracker data over to a Google account once the service is live, so you can keep all of your existing records and fitness trends. Google also says that it will keep this data private and that it won't use it for ads targetting purposes. 

What's more, Google won't just switch off Fitbit accounts without warning. In its support pages it says it will be "transparent with our customers about the timeline for ending Fitbit accounts through notices within the Fitbit app, by email, and in help articles."

You should get plenty of notice and multiple reminders between now and when the Fitbit accounts are terminated in 2025. 

For new customers yet to buy a Fitbit, from 2023, signing up to a new Fitbit account won't be available. Once the Google accounts option is live, that will become the de facto way to set up a new account when registering and activating a new Fitbit device. 

The information was shared by Fitbit in an update to one of its support pages about the migration, and more will be provided when the Google accounts go live for Fitbit.