Apple's shared documentation on monitoring geofences and iBeacon regions state within the geofencing section that there is a limit of 20 monitored regions for a single app:
For this reason, Core Location limits to 20 the number of regions that may be simultaneously monitored by a single app.
What is unclear is if this limit is for geofences and beacon regions combined, or if each type will have a limit of 20.
Are the 20 regions a shared limit? Or can I register 20 of each?