CardDAV is a protocol for syncing contact information, typically from personal devices like phones to services or web servers, such as your own website.
Server Software Support
- Radicale is a Python/WSGI implementation of CalDAV and CardDAV, and also does sync over WebDAV and basic HTTP(S). It's GPL3 licensed.
- sabre.io The open source CardDAV, CalDAV and WebDAV server.
- Baikal Baïkal is a lightweight CalDAV + CardDAV server based on PHP, SQLite and SabreDAV.
- Apple CardDAV tester: https://www.calendarserver.org/CalDAVTester.html#running-caldavtester-by-itself