Reclaim wasted space from virtual disks
OzoneMaster compacts VHD, VHDX, VMDK, VDI, and QCOW2 files — freeing real gigabytes your VM forgot to return. Works with WSL, Docker, VMware, VirtualBox, and Hyper-V.
Everything you need
Smart Compaction
Hyper-V Optimize-VHD, diskpart compact, qemu-img — the best available tool is used automatically.
Offline First
Main mode disables internet entirely during disk operations. Network only re-enables in Update mode.
RSA Protected
TOTP MFA, RSA-4096 device key pairs, and PBKDF2 credentials — all stored locally on your device.
WSL & Docker
Automatically detects WSL ext4.vhd and Docker virtual disks and includes them in scans.
History & Stats
Every scan and optimization is logged in a local SQLite database with reclaimable space tracking.
Auto Updates
Silent background updates via GitHub Releases. No uninstall needed — files update in-place.
Built for security-conscious users
Most disk tools require constant internet access. OzoneMaster works completely offline during sensitive disk operations, with internet only enabled when you explicitly switch to Update mode.
- No telemetry — zero data sent during Main mode
- RSA-4096 device authentication — tamper-proof license
- Local MFA — TOTP codes stored only on your device
- Signed offline tokens — Pro works without internet for 7 days
- User data never touched by updates or reinstallation
Simple, transparent pricing
One app. Two tiers. No usage limits.
- .vhd / .vhdx optimization
- WSL & Docker detection
- MFA local login
- Optimization history
- —.vmdk / .vdi / .qcow2
- —Priority support
- Everything in Free
- .vmdk / .vdi / .qcow2
- 7-day offline token
- Priority support
- Everything in Pro Monthly
- Best value — save ₹34/mo
- Dedicated support
Frequently asked questions
Does OzoneMaster require an internet connection?
No. Main mode blocks all internet access during disk operations. Internet is only enabled when you manually switch to Update mode for updates and license verification.
What happens when my Pro subscription expires?
Your account automatically downgrades to Free tier. VHD/VHDX optimization remains available. VMDK, VDI, and QCOW2 formats require an active Pro subscription.
Can I use Pro offline?
Yes. When online, OzoneMaster issues a signed 7-day offline token. During those 7 days you can use Pro features without internet. The token is capped at your subscription expiry date.
Is my data safe?
Your credentials, MFA codes, and offline tokens are stored only on your device. The app uses RSA-4096 key pairs for device authentication and TOTP for local MFA.
What formats does the free tier support?
Free tier supports .vhd and .vhdx files — the formats used by Hyper-V, WSL, and Docker Desktop. Pro tier adds .vmdk (VMware), .vdi (VirtualBox), and .qcow2 (QEMU/KVM).
Start optimizing for free
Download OzoneMaster for Windows or Linux. VHD/VHDX optimization is free forever. Upgrade to Pro for VMDK, VDI, and QCOW2 support.