CardDAV

CardDAV
Name	CardDAV
Developer	IETF
Released	2011
Latest release	RFC 6352
Operating system	Cross-platform
Genre	Address book access protocol
License	RFC

CardDAV is an Internet standard protocol for synchronizing contact data between clients and servers. It builds on widely deployed Internet protocols and specifications to provide address book storage, access control, and synchronization for desktop, mobile, and server software. CardDAV is defined by an IETF RFC and is implemented across many Apple Inc. products, Google LLC services, and open-source projects such as Mozilla Foundation projects and KDE applications.

Overview

CardDAV derives from several standards and integrates with established protocols to enable remote contact management across platforms such as Microsoft Corporation systems, Apple Inc. devices, and Linux distributions. The design leverages specifications produced by the Internet Engineering Task Force and interacts with formats and services associated with organizations including the World Wide Web Consortium, Open Mobile Alliance, and legacy initiatives from Nokia. CardDAV enables synchronization of contact collections hosted by servers run by entities like Yahoo! Inc., FastMail, and institutional deployments by organizations such as University of Cambridge IT services or enterprise solutions from IBM and Oracle Corporation.

Protocol and Architecture

CardDAV is an extension of WebDAV, which itself is an extension of HTTP developed by bodies like the Internet Engineering Task Force and the World Wide Web Consortium. It uses HTTP methods defined in standards associated with institutions such as European Organization for Nuclear Research discussions on RESTful design and follows conventions established in RFCs authored by contributors from organizations like Microsoft Corporation and Cisco Systems. Server-side implementations often integrate with storage backends from projects like PostgreSQL, MySQL, or directory services rooted in OpenLDAP and enterprise solutions like Active Directory from Microsoft Corporation. Clients include native mail and contacts apps from Apple Inc., Google LLC web clients, and third-party software from vendors such as Mozilla Foundation, KDE, and Evolution maintainers.

Data Model and Formats

CardDAV stores address book entries using the vCard format standardized by the Internet Engineering Task Force and originally developed through collaboration that included contributors from Nokia, Ericsson, and Sony Ericsson. The vCard data is transported within WebDAV resources and organized into collections analogous to folders familiar to users of Microsoft Exchange Server and Google LLC Contacts. Metadata and properties rely on XML and HTTP header conventions influenced by work at the World Wide Web Consortium and widely used in software by Apple Inc. and Mozilla Foundation. Interactions with calendar formats such as iCalendar — standardized through the Internet Engineering Task Force and adopted by projects like Mozilla Calendar Project — occur when contact and scheduling integration is required.

Authentication and Security

CardDAV typically relies on HTTP authentication mechanisms standardized by the Internet Engineering Task Force, including Digest and Basic auth, and more secure transports using TLS as defined by the Internet Engineering Task Force and implemented in stacks from OpenSSL and GnuTLS. Deployments integrate single sign-on and identity federation technologies developed by organizations such as Microsoft Corporation (Active Directory Federation Services), Okta, Inc., and initiatives like SAML and OAuth 2.0 promulgated by consortiums including the IETF and commercial providers like Google LLC. Server implementations incorporate access control models influenced by WebDAV ACL specifications and enterprise policies used by vendors such as IBM and Oracle Corporation.

Implementations and Clients

Server software that supports CardDAV includes open-source projects maintained by communities around SabreDAV maintainers, distribution packages in Debian and Red Hat ecosystems, and commercial offerings from Zimbra and Microsoft Corporation integrations. Client-side support exists in Apple Inc. Contacts, Mozilla Foundation-based mail clients, KDE Kontact, Evolution from the GNOME Project, and mobile clients on platforms maintained by Google LLC and Apple Inc.. Synchronization services provided by companies such as FastMail and Proton AG integrate CardDAV with webmail and hosted directory services used in enterprises by customers including Salesforce integrations and educational deployments at institutions like Massachusetts Institute of Technology.

Interoperability and Extensions

CardDAV interoperability is influenced by related standards and extensions from the IETF and the W3C, including address book extensions, calendar interoperability with CalDAV specifications, and vendor-specific profiles produced by companies such as Apple Inc. and Google LLC. Implementations often add support for server-side features that reference schema work from OpenLDAP or integration layers developed by projects like DAViCal and Radicale. Third-party extensions and synchronization helpers are provided by toolchains maintained by groups around Nextcloud, ownCloud, and community projects hosted on platforms like GitHub and GitLab.

History and Adoption

CardDAV was standardized in the early 2010s through an IETF process involving contributors from organizations including Apple Inc., Google LLC, and open-source communities around KDE and Mozilla Foundation. Its adoption accelerated as mobile platforms from Apple Inc. and Google LLC integrated synchronized contacts, and as hosting providers like FastMail, Yahoo! Inc., and enterprise vendors such as Zimbra and IBM offered hosted directory services. Academic and government deployments at institutions like University of Cambridge and Massachusetts Institute of Technology contributed to broad interoperability testing, while community projects such as ownCloud and Nextcloud extended CardDAV into private cloud solutions.

Category:Internet standards