Editor's Review
Anyone running Nextcloud, Radicale, Baïkal or a mail server with calendaring eventually hits the same wall: Android will happily sync a Google account and very little else. This app removes that wall. It registers itself as a system account provider, so a CalDAV calendar or CardDAV address book from your own server appears inside the stock Calendar and Contacts apps, and inside anything else that reads them.
Configuration decides whether you get on with it. Point the app at a base URL, supply credentials or an OAuth login where the provider requires one, and it discovers the collections on offer, letting you pick which calendars and address books to sync and how often each is checked. WebDAV shares can also be exposed to the Android file picker, while task lists work through a compatible tasks app rather than natively, because Android has no task store of its own.
The project is open source and the paid listing funds development rather than unlocking anything hidden. Both the 4.3 average and the modest 100K+ install count match the audience: people who already know what CardDAV means and want it to work properly. Budget some time for the first setup, particularly with self-signed certificates or unusual server paths, and expect aggressive battery optimisation on certain phones to stall scheduled syncs until the app is exempted.
Features
CalDAV calendar sync into the Android system calendar
CardDAV contact sync into the system address book
WebDAV shares exposed to the Android storage picker
Automatic discovery of collections from a single server URL
Selective syncing with per-collection intervals
Pros
Native integration, so synced data shows up in the apps you already use
Works with any standards-compliant server instead of one vendor
Open source, with the purchase supporting the project directly
Fine control over what syncs and how frequently
Cons
Setup assumes you understand your own server configuration
Battery optimisation on some handsets quietly stalls scheduled syncs
Questions people ask
Do I need my own server?
Yes. This is a sync client, so it needs a CalDAV or CardDAV service behind it, whether that is Nextcloud, a mail provider that supports the standards, or something you host yourself.
Does it handle task lists?
Tasks are supported, but you need a compatible tasks app installed alongside it, because Android provides no built-in store for them.
Why is the store listing paid?
The code is open source and the price funds continued development rather than unlocking extra features.
Will synced contacts appear in the normal Contacts app?
Yes. Because it registers as an account provider, the synced calendars and contacts turn up in the stock apps and in anything else that reads system accounts.
