DAVKeep

Contacts and calendars from your own server — through a gate only your key opens.

DAVKeep is an Android sync provider for CalDAV and CardDAV. It fills the phone's own Contacts and Calendar apps, so everything that reads them reads your server. There is no separate address book to learn and nothing to open.

It exists for one case the usual clients do not cover: a DAV server behind an identity-aware proxy. Each account can carry its own HTTP headers — a Cloudflare Access service token, say — and its own client certificate, from the Android KeyChain or imported from a .p12.

What it does

Two-way sync: an edit made in the stock Contacts or Calendar app reaches the server.
Per-account custom headers and mTLS, including servers that demand both.
Write-back that patches the server's own vCard or .ics, so properties Android cannot model — X- fields, VTIMEZONE, alarms it does not understand — survive an edit that never touched them.
A Collection is read-only until you say otherwise.

What it looks like

The accounts screen: one account reading OK, with three Collections listed under it. — One card per account, one line per Collection.

A Collection's own screen, with switches for syncing it and for sending edits back. — Sending edits is per Collection, and off until you turn it on.

Account setup: custom headers, a client certificate from the KeyChain, username and password. — Headers and a client certificate, per account.

The log screen, listing each sync with what it wrote and deleted. — Every run, in words, kept on the phone.

It tells you when it fails

Silent failure is the thing this app is built against. Every run says what it did, in words, and a sync that could not finish never claims it did:

ok written=1 deleted=0 uploaded=1 sent 1 edit to the server
WARN 1 edit was replaced by the server's version: the server's copy had changed
ERROR the server cut the listing short: nothing was deleted, and nothing was recorded

Get it

Download APK Add to Obtainium Source Issues

Android 7.0 and later. There is no Play listing. Obtainium is the way to get updates without one: the button hands it this repository, and it watches the releases from then on. Obtainium is itself free software.

Releases are signed with the project's own key. A build installed from here cannot be replaced by one built by anyone else — including, if it is ever listed there, F-Droid's own build, which F-Droid signs itself. Switching between them means uninstalling, so export your accounts first.

Application id app.davkeep. Free software under GPL-3.0-or-later, developed in the open. No analytics, no ads, no update check: it talks to your servers and to nothing else.