# Limitations

VaultLink works well for most Obsidian vaults, but has some constraints you should know about.

## File Type Limitations

### Mergeable Files

Only **`.md`** and **`.txt`** files get automatic conflict-free merging.

Other file types (images, PDFs, etc.) use last-write-wins:

```
User A updates diagram.png → Server stores version 1
User B updates diagram.png → Server stores version 2 (overwrites A's changes)
```

**Workaround**: Avoid editing the same non-text file simultaneously.

### Binary Detection

Files are treated as binary if they:

- Contain NUL bytes (`0x00`)
- Fail UTF-8 validation

Binary files within `.md` or `.txt` extensions still get last-write-wins (no merge).

## Performance Constraints

### Server Limits (Configurable)

| Resource                 | Default | Maximum Tested |
| ------------------------ | ------- | -------------- |
| Clients per vault        | 256     | ~256           |
| Database connections     | 12      | 20             |
| Max file size            | 512 MB  | 4096 MB        |
| Request timeout          | 60s     | 180s           |
| WebSocket cursor timeout | 60s     | 300s           |
| Database busy timeout    | 3600s   | -              |

### Vault Size

- **Small vaults** (< 1000 files): Excellent performance
- **Medium vaults** (1000-10000 files): Good performance
- **Large vaults** (> 10000 files): Works, but initial sync slower

No hard file count limit—constrained by disk space and sync time.

### Resource Usage

Rough estimates (varies by vault size and activity):

- **RAM**: ~50-200 MB base + ~1-5 MB per active client
- **CPU**: Low (< 5%) for typical usage, spikes during merges
- **Disk**: Vault size + version history (grows over time)

## Version History

### Storage

- All versions stored indefinitely (no automatic cleanup)
- Each vault is a separate SQLite database
- Deleted files marked as deleted (not purged)

**Growth**: Version history grows with every change. A 10 MB vault with frequent edits might grow to 100+ MB over months.

**Cleanup**: Manual only (see [Advanced Configuration](/config/advanced#version-history-cleanup)).

### Implications

- Disk usage grows over time
- Database size affects backup time
- No built-in retention policy

## Merge Quality

### Text Merging

VaultLink uses word-level tokenisation for merging:

```markdown
Parent: "The quick brown fox"
User A: "The quick red fox"
User B: "The very quick brown fox"
Result: "The very quick red fox" ← Both changes preserved
```

**Imperfect scenarios**:

- Complex nested Markdown (tables, code blocks)
- Simultaneous edits to the same sentence
- Large structural changes (moving sections around)

**Result**: Merged file might need manual cleanup in ~1-5% of concurrent edits.

## Scalability

### SQLite Limitations

- One SQLite database per vault
- Single-server architecture (no built-in clustering)
- Write serialisation through database

**For high concurrency**: Consider multiple vaults instead of one massive shared vault.

### Horizontal Scaling

Not currently supported. Running multiple servers requires manual vault partitioning.

## Network Requirements

### Latency

- Real-time sync typically < 500ms on good connections
- Mobile/slow networks: 1-5s latency possible
- Timeout failures on very slow connections (> 60s)

### Offline Behaviour

- Clients queue changes locally
- On reconnect, sync all changes since last connection
- Conflicts resolved automatically (for mergeable files)

**Limitation**: No offline conflict preview—merged result appears after reconnect.

## Security

### No End-to-End Encryption

- Server sees all file contents
- Transport encryption only (WSS/TLS)
- Trust your server

**Workaround**: Self-host on infrastructure you control.

### Authentication

- Token-based only (no OAuth, SAML, etc.)
- Tokens configured in server config file
- No runtime user management

## Known Edge Cases

### Simultaneous Deletes and Edits

```
User A deletes note.md
User B edits note.md
Result: Edit wins (file recreated with B's content)
```

Operational transformation prioritises content preservation.

### Large File Uploads

Files > 100 MB may time out on slow connections. Increase `response_timeout_seconds` or split large files.

### Mobile Sync

- Mobile networks may drop WebSocket connections frequently
- Client auto-reconnects, but causes sync delays
- Battery impact from constant reconnections

## What VaultLink is NOT

- **Not a backup solution**: Version history helps but isn't a backup (make backups!)
- **Not Git**: No branching, no commit messages, no diffs to review before merge
- **Not encrypted storage**: Server sees everything
- **Not multi-master**: One server, multiple clients (not peer-to-peer)

## Recommendations

### Good Use Cases

- Personal multi-device sync (< 10 devices)
- Small team collaboration (< 20 people)
- Primarily text/Markdown content
- Trusted server environment

### Poor Use Cases

- Large teams (> 50 concurrent users per vault)
- Primarily binary files (images, videos, large PDFs)
- Untrusted server (need E2E encryption)
- Highly regulated environments (HIPAA, etc.)

## Next Steps

- [Server configuration limits →](/config/server)
- [Advanced tuning →](/config/advanced)
- [Architecture details →](/architecture/)