WebDAV-sync

Android app that keeps local folders and WebDAV remote folders in sync — manually, on a schedule, or when files change.

Current release: v1.1.3
Min Android: 8.0 (API 26)
License: MIT

Features

• Multiple WebDAV accounts with Basic or Digest authentication (auto-detected)
• Folder pairs linking a local SAF folder to a remote path
• Sync methods
  • Two-way — three-way baseline sync with conflict copies
  • To the device — remote → local only
  • To the cloud — local → remote only
• Background sync via WorkManager (periodic + manual + boot reschedule), with a flex window and “battery not low” by default
• Instant upload when local changes are detected (optional per pair), coalesced so it never interrupts an in-flight pass — off by default on new installs
• Battery saver profile (Wi‑Fi only, charging only, 3-hour interval, no sync-on-local-change)
• Foreground notification with pause / resume / cancel only while a pass is talking to the server
• Live Recent changes on Overview while a pass is running (upload / download / delete counts, no DB write per file)
• Size limits for upload and download
• Wi‑Fi only, mobile-data warning, parallel transfers, retries
• Quota display (RFC 4331) on Overview when the server supports it
• Home-screen widget (4×1): status, recent change counts, Sync button
• Color-coded sync status — OK (green), in process (yellow), ERROR (red) on Overview and widget
• Encrypted credentials (EncryptedSharedPreferences / Keystore)
• Backup & restore of accounts and folder-pair configuration
• Optional custom CA for self-signed / private servers
• Diagnostic logging (redacted) for troubleshooting

Screens

Tab	Purpose
Overview	Last sync, duration, status, recent changes, cloud storage
Folders	Folder pairs, enable toggle, add/edit
Settings	Sync options, network, backup/restore, about

Getting started

1. Install the APK from Releases, or build from source (below).
2. Open Settings → Accounts (or add an account when creating a folder pair) and enter your WebDAV URL, username, and password.
3. On Folders, add a folder pair: pick the remote path, local folder (SAF), and sync method.
4. Tap Sync on Overview, or wait for the scheduled interval / instant upload.

Default remote path suggestion: /Webdavsync.

Build from source

Requirements

• JDK 17+
• Android SDK (compile/target SDK 35)
• Optional: a release keystore for signed builds

Debug

./gradlew :app:assembleDebug
# APK: app/build/outputs/apk/debug/WebDAV-sync-*.apk

Release (signed)

Create keystore.properties in the project root (gitignored):

storeFile=release.keystore
storePassword=...
keyAlias=...
keyPassword=...

./gradlew :app:assembleRelease
# APK: app/build/outputs/apk/release/WebDAV-sync-{version}.apk

Unit tests

./gradlew :app:testDebugUnitTest

Architecture (short)

Layer	Stack
UI	Jetpack Compose, Material 3, Navigation, Hilt ViewModels
Sync	WorkManager foreground worker, three-way diff, SAF I/O
WebDAV	Sardine-Android (OkHttp): PROPFIND, PUT, GET, DELETE, MKCOL, quota
Storage	Room (pairs, baseline, logs), EncryptedSharedPreferences (secrets)

Core flow: scan local + remote → diff against last-sync baseline → transfer/delete → update baseline → log session totals for Recent changes.

Privacy

• Credentials stay on device (encrypted).
• No analytics or third-party tracking SDKs in this project.
• Network traffic only goes to the WebDAV servers you configure.

Contact

• Email: hummersoft@mailbox.org
• Issues: GitHub Issues

Changelog (recent)

v1.1.3

• Lower idle battery use — local change detection no longer walks the whole SAF tree every 4 seconds. Instant upload uses ContentObserver + a WorkManager content-URI trigger, with a cheap 90s root query as fallback. Periodic sync remains the safety net.
• Safer new-install defaults — “Sync immediately on local changes” is off; scheduled work waits until the battery is not low (manual Sync still runs). Periodic jobs use a flex window so Android can batch them. Existing saved settings are unchanged.
• Battery saver profile on Synchronization settings: Wi‑Fi only, only while charging, 3-hour interval, instant-on off. Configuration copy explains that Unrestricted battery is only needed for instant upload.
• Idle “To the cloud” passes skip the network — after a successful pass the local tree fingerprint is stored; if it is unchanged, the next to-cloud tick does not PROPFIND, MKCOL, or show a sync notification.
• Foreground service only when needed — no persistent notification for an all-idle tick. Quota refresh and empty-folder cleanup are skipped or limited to folders that just lost files.
• Edit folder pair keeps Last sync — saving a pair no longer wipes Last sync / Duration / Status (unless the local or remote path changed).

v1.1.2

• Live Recent changes on Overview — while a sync is running, Upload / Download / Deleted in device / Deleted in cloud update in real time from in-memory counters (SyncProgress). Section title shows Recent changes (live); when the pass ends, counters return to the last finished session summary from Room.
• No per-file database writes for progress — only atomics + StateFlow (same file counts as the session summary; conflicts that upload/download count as up/down).

v1.1.1

• Fix large multi-file upload hang — batches of ~100MB–GB (e.g. many ~30MB FLACs) no longer freeze after “Executing transfers…” with zero PUTs on the server. Root cause: parallel full-file staging into app cache under parallel=4 exhausted SAF I/O/memory.
• Streaming WebDAV PUT — upload streams from SAF with known Content-Length; the stream is reopened on Digest/OkHttp writeTo retries (no multi‑100MB temp copies).
• Auto-throttle upload concurrency — heavy upload batches (large files / high count / high total bytes) run with parallel=1 so mobile sync stays reliable.
• Unicode path support confirmed — Cyrillic and other non-English folder/file names (e.g. !Мой сборник) upload correctly via percent-encoded path segments.
• Better transfer diagnostics — dir/file phase and per-file upload/download start lines; diagnostic log also mirrors to logcat and fsyncs so a killed process leaves the last progress line.
• Code structure cleanup — shared SyncOverviewMetrics, ManualSyncStarter, SettingToggleRow / AppScaffold, RelativePaths, SyncEngine.finishPair, unified Overview/widget status colors (SyncStatusDisplay.ColorRole).
• Verified on device: 61 files / ~755MB uploaded successfully (mixed FLAC + Cyrillic MP3 paths) in ~74s with status OK.

v1.0.19

• Stop nested “(conflicted copy)” cascade — timed-out uploads no longer leave partial remotes that the next pass treats as new conflicts; incomplete PUT/GET is repaired by re-uploading/downloading the larger side; conflicted-copy paths never nest another layer; conflict copies upload in the same pass when possible
• No transfer body timeouts — OkHttp read/write timeouts removed so multi‑MB files can finish on mobile without mid-body abort
• Failed upload cleanup — truncated remote objects smaller than the local source are deleted so the next pass retries a clean PUT
• Overview and widget Status stay in sync — shared SyncStatusDisplay (same labels: OK / ERROR / “Sync in process…” / Ready); widget no longer freezes on sticky “Syncing…” after ERROR
• Mobile-data warning works with VPN — cellular detection checks all networks (not only the active VPN interface); widget Sync opens Overview for the same confirm dialog
• Manual-only mobile warning documented in-app via (i) info popups (Wi‑Fi only, warn on mobile, parallel transfers, retry attempts)
• UI polish — Overview/About product title Web + gray DAV + -Sync at 26sp; info icons gray and inline at the end of multi-line labels

v1.0.17

• True single-flight sync across manual + periodic workers — WorkManager can start both unique works at once; only one may own a session (tryBeginSession). Concurrent downloads of the same path no longer race SAF createFile into name (1).ext ghosts that the next pass then uploads.
• SAF create rejects auto-renames — if the provider renames a create to file (1).jpg or Photos (1), the ghost is deleted and the canonical name is re-resolved so content is never written under an untracked path.
• Overview Status no longer sticks on “Sync in process…” after a finished pass — only a RUNNING worker counts as syncing (ENQUEUED waiting on Wi‑Fi/charging no longer masks Last sync / Duration as still in progress).
• Widget stays aligned with Overview during chained follow-ups (keeps “Syncing…” when a follow-up is enqueued; reloads also check WorkManager RUNNING).
• Large multi-file re-syncs are much faster when the trees already match (no concurrent double-pass / phantom uploads).

v1.0.16

• Idle follow-up does not overwrite Last sync / Duration / Recent changes — a short no-op pass after a real multi-minute sync no longer shows “duration: 1s” or zeros out counters
• Includes the v1.0.15 single-flight / mid-sync race fixes

v1.0.15

• Fix large multi-file sync race: local folder watch no longer cancels an in-flight sync when downloads rewrite the tree (that caused duplicate uploads, conflicted copies, and stuck “Sync in process…”)
• Single-flight WorkManager passes with one coalesced follow-up instead of REPLACE mid-transfer
• Two-way size match after download ignores SAF vs remote mtime skew (false conflicts)
• Remove partial local files if a download is cancelled mid-stream
• Status colors on Overview and home widget: OK / Ready green, syncing yellow, ERROR red
• SAF name sanitization for remote names rewritten by local storage (e.g. ? → _)
• Widget Sync button styling polish; contact email update

v1.0.12

• Fix Recent changes for multi-folder sync (session-wide upload/download/delete totals)
• Always record complete counter batches (including zeros)
• Home widget and Overview share the same aggregation logic
• Various sync, quota, duration, path-encoding, and UI fixes since v1.0.4

See Releases for assets and full notes.