CardDAVCalDAVSchnittstellen

CardDAV and CalDAV are open standards for accessing and managing contact and calendar data on remote servers. CardDAV provides access to address books using the vCard data format, while CalDAV provides access to calendars using the iCalendar data format. Both protocols extend WebDAV over HTTP and are defined in separate RFCs: CardDAV (RFC 6352) for vCard-based contacts and CalDAV (RFC 4791) for iCalendar-based calendars. The terms CardDAVs and CalDAVs are sometimes used informally to refer to using these protocols over TLS-secured connections (HTTPS).

How they work is to expose server resources that represent address books and calendars. Clients communicate with these resources using standard WebDAV and HTTP methods, such as PROPFIND, REPORT, PUT, and GET. The stored data are encapsulated in vCard 4.0 objects for CardDAV and VCALENDAR objects for CalDAV. Synchronization relies on WebDAV mechanisms and can utilize ETags and other state-tracking features. CalDAV additionally supports calendar-specific features such as scheduling and free/busy information through iTIP and related extensions, while CardDAV supports sharing, access control, and group addressing within address books.

Implementation and interoperability: CardDAV and CalDAV are widely supported by servers and clients across platforms. Examples include open-source solutions like Radicale and SabreDAV-based servers, and popular deployments in Nextcloud or ownCloud ecosystems, as well as native clients on iOS and macOS and various Android and desktop applications. The standards promote cross-platform synchronization of personal data without vendor lock-in. Security is commonly achieved through HTTPS, ensuring encrypted transmission of credentials and data.