Are my iPhone / iPad backups safe if I delete the 2Do app?

Local backups are deleted with the app. Uploaded iCloud Drive copies remain available.

In 2Do 4.3.4 or later, open Settings > Backups & Export and turn on Save Backups to iCloud Drive. This option is off by default. It adds copies of your retained .2dodb archives and new backups to iCloud Drive while keeping local backups as before.

Before deleting 2Do, tap Create Backup Now and wait until the status shows the latest backup in iCloud Drive. A file that is still waiting to upload does not yet protect against app deletion. iCloud Drive must be enabled for 2Do, with enough storage available.

After reinstalling, use the same Apple Account and open Settings > Backups & Export > Restore from File…. Choose a backup under iCloud Drive > 2Do > Backups, then restore selected lists or the whole database. See Restore from iCloud Drive After Reinstalling for the steps and the effect of each restore option.

On earlier versions, or if you prefer another destination, use Backup to Email or a stored backup's Save a Copy… action to keep a copy outside the app.

See Backups for the full guidance.