Regardless of user permissions, up to 4 devices per account (※1), or up to 8 devices if you have a Teachme Player subscription,
can be logged in simultaneously.
If access is attempted from devices exceeding the limit (※2), devices with the oldest last access time will be forcibly logged out first.
Errors displayed when forcibly logged out
- Web browser version: You are not logged in to Teachme. Please log in and try again.

- Mobile app (iOS): Authentication error. Re-login required.
- Mobile app (Android): Authentication error. Re-authentication required.

- Mobile browser: Cannot read properties of undefined (reading 'map')

Notes
※1
If you are subscribed to the legacy plan "Teachme Biz Basic Plan," there is no limit on the number of connected devices.
※2
Each application (Teachme Biz or Teachme Player) is counted as one device per connection source.
Example)
If a single PC is used to access Teachme Biz from both Google Chrome and Microsoft Edge, the number of connected devices is counted as 2.
If a single smartphone is used to access Teachme Biz via both the Teachme Biz app and the Teachme Player app, the number of connected devices is counted as 2.
Related: What should I be aware of when sharing an account among multiple users?
https://help.teachme.jp/hc/en-us/articles/4411464955673