1. Introduction
1.1. What is DAVx⁵?
DAVx⁵ is a CalDAV/CardDAV client (management and sync app) for Android. It allows you to
manage CalDAV/CardDAV collections (address books, calendars, task lists) on your server and
synchronize them with your Android device (to be specifically, with the storage backends of the device, see illustration below),
access your WebDAV files.
DAVx⁵ is not:
a storage backend – This means that your contacts, events and tasks will not be stored within the DAVx⁵ app but in the respective content providers.
a contacts, calendar or tasks app – You still need separate apps to view and edit your contacts, events and tasks. You can use any app that uses the Android Contacts/Calendar Provider for contacts/calendars and an OpenTasks provider for tasks.
a backup tool – You can use DAVx⁵ to transfer your data to a server, but make sure to perform server backups on a regular basis. Just imagine that an app you have installed deletes all contacts on your phone: DAVx⁵ will synchronize these deletions as expected and all contacts will be gone on the server, too.
DAVx⁵ is the interface between the local storage (which is used by the end-user apps) and the CalDAV/CardDAV service.
1.2. First steps
How to start using DAVx⁵ on your Android device:
Download and install DAVx⁵.
Open DAVx⁵.
Follow the instructions of the start screen (permissions, battery saving etc.).
Tap on “⊕ Add account” to add a new account.
Login using provider-specific login (preferred if supported) or base URL / email address and login credentials. You can get the base URL from your service provider and/or our list of tested services.
Finish the steps to add the account.
Select the address books and calendars/task lists you want to synchronize so that the respective switches are enabled.
Force sync (”🗘 Synchronize”) if you want the data to be available immediately.
Access your address books, events and tasks using your favorite apps (Contacts, Calendar, OpenTasks, …).
When you create a contact/event, select the desired DAVx⁵ account as storage location. Local contacts/events will stay on your phone and not be synchronized. If you’re using DAVx⁵ the first time, you may want to transfer your local contacts to the CardDAV server.
On some devices (like Huawei and Xiaomi), additional steps are required to allow DAVx⁵ to run automatically.
1.3. Authentication
1.3.1. Provider-specific login
When you choose provider-specific login, DAVx⁵ uses
OAuth for Fastmail and Google, and
Login Flow for Nextcloud.
These authentication methods don’t transfer the username and password for every request, but use a token and/or app password instead.
Hint
If there’s a provider-specific login option for your provider, you should prefer it for maximum security, automatic compatibility with 2FA and automatic presets (like contact group type).
1.3.2. User name / password
When this authentication method is used, your user name (usually your email address) and password will be sent to the server with every request.
If possible, it’s recommended to use an app password instead of your account password. Services often require/allow app passwords as a fallback when two-factor authentication (2FA) is activated.
An app password is a server-generated random password that is only intended for a specific client and that can be used as a password substitute. By using a separate app password for each app — like DAVx⁵ — you can keep your account password private and revoke access per app at any time.
To use an app password, this needs to be supported by the service. Usually you can visit the Web interface of your service and look for something like Authentication settings / Create app password. Then create an app password for DAVx⁵ and enter that app password instead of your account password in DAVx⁵.
1.3.3. Client certificates
You can provide a TLS client certificate for authentication, either alone or together with username/password. To use a client certificate, first install it to your device, and then choose it in Advanced login.
1.3.4. Anonymous
DAVx⁵ supports anonymous CalDAV/CardDAV access (usually for read-only servers) if you choose Advanced login and then don’t enter any credentials.
1.4. Permissions and battery optimization
DAVx⁵ requires various Android permissions in order to perform its task. It will ask for contacts, events and task access permissions.
DAVx⁵ will also ask about being whitelisted from battery saving. Since Android 6, Android has two features called doze and app standby which reduce battery usage by restricting apps which are not interactively used at the moment. This will also disable synchronization for apps unless they’re actively used or the device is connected to a power supply.
Note
If you want DAVx⁵ synchronization to be run in regular intervals in the background, DAVx⁵ must be exempt from “battery saving”! This does not mean that DAVx⁵ requires more battery than it should, but only that you allow DAVx⁵ to run in the background for synchronization.
Some devices (e.g. Huawei) also have a vendor-specific autostart permission, which must be granted for DAVx⁵ to work. See the FAQ entry about automatic synchronization for more information.
1.5. Glossary
Some important terms to better understand how DAVx⁵ works:
- WebDAV
HTTP-based protocol to manage remote resources (≙ files/directories) and collections (≙ directories). WebDAV collections may contain member resources. Provides methods to list, upload, modify, delete resources and their metadata; locking, access permissions (ACL) etc.
- CalDAV
Extension for WebDAV to process events (VEVENT) and tasks (VTODO) in iCalendar format. CalDAV servers semantically understand and process entries and can – for instance – filter events so that only events within a certain time range are delivered.
- CalDAV Scheduling
An extension for CalDAV for performing scheduling operations like inviting other people to events, managing attendees and their participation status etc.
- Calendar provider
On Android devices, there is a database where calendars/events are stored. This database belongs to a system app called Calendar provider. To access the calendars and events, apps communicate with the Calendar provider.
- CardDAV
Extension for WebDAV to process contacts in vCard format. CardDAV servers semantically understand and process entries.
- Collection
A folder where iCalendar/vCard resources are stored. In CalDAV, collections are calendars/task lists; in CardDAV, they’re address books.
- Contacts provider
On Android devices, there is a database where contacts are stored. This database belongs to a system app called Contacts provider. To access the contacts, apps communicate with the Contacts provider.
- iCalendar
File format to exchange events, tasks, journal entries and busy-time information. Cares about time zones, date/time formats, recurring events and exceptions etc. DAVx⁵ maps Android events and tasks to iCalendar resources and vice versa. Every event/task is stored as a separate iCalendar resource (“.ics file”) on the server.
- vCard
The “electronic business card” is a file format to exchange contact and contact group information. CardDAV servers are required to support at least vCard 3, but for some advanced features, vCard 4 is needed. DAVx⁵ maps Android contacts and contact groups to vCard resources and vice versa. Every contact is stored as a separate vCard resource (“.vcf file”) on the server.