UniDrive — Linux Cloud Sync Comparison

What sets UniDrive apart

Features that most Linux sync tools lack entirely.

⇄ Real bidirectional sync

Three-phase engine: Gather (delta + local scan) → Reconcile (move detection, conflicts) → Apply (dependency-ordered actions). Not a polling loop or manual copy.

☷ Sparse file placeholders

Files appear at full size but consume zero disk blocks. Hydrate on demand with get, reclaim space with free. No FUSE dependency.

⥂ Move detection

Detects rename/move by matching Delete+Create pairs via remote ID. Folder moves propagate to children automatically — no re-upload.

⚖ Conflict resolution

Per-folder policy: keep_both (creates .conflict-remote copy) or last_writer_wins (mtime comparison). Not a silent overwrite.

⚙ 6 provider types

OneDrive, HiDrive, Internxt, S3-compatible (AWS, Hetzner, Backblaze, Wasabi, OVH, MinIO), SFTP, and WebDAV — one engine, one config.

⇅ Size-tiered concurrency

16 slots for small files (≤1 MB), 6 for medium, 2 for large. Optimizes throughput without saturating the connection on big files.

★ Pin rules (glob patterns)

Eager-download files matching *.kdbx, Documents/work/**. Include/exclude lists. Custom regex-safe glob engine.

👁 inotify + echo suppression

Daemon mode watches for local changes between sync cycles. Sync-caused events suppressed automatically to prevent loops.

🔒 Client-side encryption

Internxt provider: AES-256-GCM names, AES-256-CTR content, BIP39 key derivation. Streaming encrypt/decrypt — peak RAM ~256 KB.

Feature comparison // all Linux sync tools

Side-by-side across open source, freemium, and proprietary solutions.

Tool	License	Price	Providers	Bidir Sync	Placeholders	Move Detect	Conflicts	Client Encrypt	Delta Sync	Bandwidth Ctl	Pin / Selective	CLI	GUI
UniDrive	OSS	Free	6 types	✓ 3-phase	✓ sparse	✓ ID+size	✓ per-folder	✓ AES-256	✓ cursor+snapshot	✓ throttle	✓ glob pins	✓	planned
rclone	MIT	Free	70+	bisync (stable 2025)	✗ FUSE mount	✗	basic	✓ NaCl crypt	partial	✓	filters	✓	web UI
Syncthing	MPL-2	Free	P2P only	✓	✗	✗	✓	untrusted device	✓ block-level	✓	✓ ignore	✓	✓ web
Nextcloud	GPLv2	Free	Nextcloud only	✓	experimental	✗	basic	server E2EE	✓	✗	✓ selective	nextcloudcmd	✓ Qt
ownCloud	GPLv2	Free	ownCloud only	✓	✓ VFS	✗	basic	server-side	✓	✗	✓ selective	owncloudcmd	✓ Qt
onedrive (abraunegg)	GPLv3	Free	OneDrive only	✓	✗	✗	basic	✗	✓ delta API	✓	✓ skip_dir	✓	✗
Maestral	MIT	Free	Dropbox only	✓	✗	✗	✓	✗	✓ longpoll	✓	✓ gitignore	✓	✓ tray
FreeFileSync	GPLv3	Free	local/FTP/SFTP	✓ manual	✗	✓	✓	✗	comparison	✗	✓ filters	batch	✓
Internxt CLI	OSS	Freemium	Internxt only	✗ manual	✗	✗	✗	✓ AES-256	✗	✗	✗	✓	✗
Internxt Desktop	OSS	Freemium	Internxt only	FUSE write-back	FUSE mount	✗	byte compare	✓ AES-256	✗ full poll	✗	✗	✗	✓ Electron
Dropbox	Proprietary	Freemium	Dropbox only	✓	✗ Linux	✓	✓	✗	✓ block-level	✓	✓ selective	✓	✓
MEGA	Custom	Freemium	MEGA only	✓	✗	✗	basic	✓ AES-128 E2EE	✓	✓	✓ selective	✓ mega-cmd	✓
pCloud	Proprietary	Freemium	pCloud only	✓	✓ FUSE vdrive	✗	basic	Crypto add-on	✓ block-level	✗	✓ selective	pfs CLI	✓
Tresorit	Proprietary	from $4.75/mo	Tresorit only	✓	✗	✗	basic	✓ E2EE	✓	✗	✓ selective	✓	✓
Insync	Proprietary	~$30/acct	GDrive, OneDrive, Dropbox	✓	✗	✗	basic	✗	✓	✗	✓ selective	✓ headless	✓ Qt
ExpanDrive	Proprietary	Free personal	20+	✗ mount only	✓ net mount	✗	✗	✗	✗	✓	✗	✗	✓

✓ = full support partial/limited ✗ = no support Data as of April 2026.

UniDrive provider support

One sync engine, six provider types, dozens of backends.

Microsoft OneDrive

Personal & Business. MS Graph delta API for efficient change tracking.

OAuth2 (browser + device code)

IONOS HiDrive

REST API v2.1 with snapshot-based delta detection.

OAuth2 (browser)

Internxt Drive

E2EE with AES-256-GCM names, AES-256-CTR content, BIP39 keys.

email + password + 2FA

S3-compatible

AWS, Hetzner, Backblaze B2, Wasabi, OVH, MinIO. SigV4 auth.

env vars (access key + secret)

SFTP

Apache MINA SSHD. Key or password auth. Auto-detect ~/.ssh keys.

SSH key / password

WebDAV

Nextcloud, ownCloud, Synology, QNAP, Hetzner Storage. HTTP Basic.

user + password

Sync engine architecture

Three-phase sync with provider-agnostic reconciliation.

┌─────────────────────────────────────────────────────────────────┐
│  GATHER                                                        │
│                                                                 │
│  Remote delta  ──────┐     ┌──────  Local scan (inotify)        │
│  (cursor or snapshot) │     │  (mtime + size vs SQLite DB)       │
│                       ▼     ▼                                   │
├─────────────────────────────────────────────────────────────────┤
│  RECONCILE                                                     │
│                                                                 │
│  ┌──────────┐  ┌───────────┐  ┌──────────┐  ┌───────────────┐  │
│  │ Move     │  │ Conflict  │  │ Case     │  │ Pin rules     │  │
│  │ detection │  │ policy    │  │ collision│  │ (glob match)  │  │
│  └──────────┘  └───────────┘  └──────────┘  └───────────────┘  │
│                       │                                         │
│                       ▼  ordered action list                     │
├─────────────────────────────────────────────────────────────────┤
│  APPLY                                                         │
│                                                                 │
│  Pass 1 (sequential)          Pass 2 (concurrent)               │
│  ┌─────────────────────┐      ┌────────────────────────────┐    │
│  │ placeholders         │      │ downloads   ≤1MB → 16 slots│    │
│  │ deletes, moves       │      │ uploads    1-20MB →  6 slots│    │
│  │ folder creates       │      │             >20MB →  2 slots│    │
│  │ conflicts            │      └────────────────────────────┘    │
│  └─────────────────────┘                                        │
│           │                              │                       │
│           └──── SQLite state DB (1 txn) ──┘                       │
└─────────────────────────────────────────────────────────────────┘

The placeholder gap on Linux

Most cloud tools can't show files without downloading them. Here's the 2026 landscape.

Tool	Placeholder / on-demand files on Linux	Mechanism
UniDrive	✓ Production-ready	Sparse files via `RandomAccessFile.setLength()` — zero disk blocks, real size in stat. No kernel module.
ownCloud	✓ Stable	Qt VFS layer with file manager integration (Nautilus, Dolphin).
pCloud	✓ Stable	FUSE virtual drive — files fetched on open. Requires FUSE kernel module.
ExpanDrive	✓ Network mount	Network filesystem mount. Files not available offline. Proprietary.
rclone mount	Approximation	FUSE mount with VFS cache modes. Not integrated into file manager. Requires FUSE.
Nextcloud	Experimental	VFS on Linux is marked experimental. Stability issues and data loss bugs reported in 2026.
Dropbox	✗ Smart Sync is Win/Mac only	Linux client lacks Smart Sync. Selective sync only (invisible if not synced).
Everyone else	✗	Syncthing, MEGA, Maestral, Insync, Tresorit, abraunegg/onedrive — no placeholder support.

Where UniDrive wins and where it doesn't // honest take

No tool does everything. Here's where UniDrive excels and where alternatives are stronger.

▲ UniDrive advantages

Only multi-provider tool with true bidirectional sync + sparse placeholders on Linux
Move detection avoids pointless re-uploads (most tools delete + re-upload)
Per-folder conflict policy — not a silent overwrite or a global setting
Snapshot-based delta for providers without native change APIs (S3, SFTP, WebDAV)
Size-tiered concurrency adapts to file mix automatically
No FUSE, no Electron, no kernel modules — pure userspace JVM binary
Pin rules with glob patterns for eager download
Case collision detection (OneDrive vs ext4)
Bandwidth throttling built into the provider layer
inotify daemon with echo suppression for near-real-time local change detection

▼ Where alternatives are stronger

rclone: 70+ providers vs UniDrive's 6 types. Massive community. Stable FUSE mount.
Syncthing: Block-level delta sync (only changed bytes). P2P with no cloud dependency.
Dropbox: Block-level sync (LAN sync, delta encoding). Mature file manager integration.
MEGA / Tresorit: E2EE enabled by default for all files, not just one provider.
Nextcloud / ownCloud: Native Qt GUI with file manager overlay icons.
Insync: Polished multi-provider GUI with headless mode. Proven at scale.
No GUI yet — CLI-only today (systray UI is Phase 3 on the roadmap)
No block-level delta — full file uploads even for small changes
No sharing, trash, or file versioning features
JVM startup overhead vs native Go/C++ tools (mitigated by daemon mode)

▬ Best-in-class for this use case

You use multiple cloud providers and want one sync tool → UniDrive
You need placeholder files on Linux without FUSE → UniDrive
You sync a NAS via SFTP/WebDAV and want bidirectional sync → UniDrive
You want zero-knowledge E2EE with Internxt from a real sync engine → UniDrive
You need maximum provider coverage (70+) → rclone
You want P2P without any cloud → Syncthing
You need a polished GUI today → Insync or native clients

The Linux cloud sync problem is still unsolved.