System requirements
What Unlost needs, and what it can scan
Unlost runs on Windows 10 and Windows 11, 64-bit. The installer is 4.0 MB. It asks for administrator rights once at startup, because reading a drive sector by sector is a privileged operation in Windows and there is no way around that for any recovery tool. You also need a second drive with enough free space to hold the files you recover, because Unlost will not write them back onto the drive it is reading.
Operating system
| Requirement | Detail |
|---|---|
| Windows version | Windows 10 or Windows 11, 64-bit. Windows Server is not tested |
| Processor | 64-bit x86 (Intel or AMD) |
| Interface runtime | The Microsoft Edge WebView2 runtime, which ships with Windows 11 and is present on up-to-date Windows 10. The installer checks for it and downloads nothing behind your back: if it is missing, the finish screen says so and offers a link to Microsoft's own download page |
| Screen | The window will not go below 900 × 620 pixels at 100% scaling, so a display smaller than that — or a large scaling setting on a small one — will clip it |
| Memory | Nothing unusual. Memory use does not grow with the drive or with the file — a fifty gigabyte video costs the same as a photograph, because nothing large is ever loaded whole. Any machine that runs Windows 10 comfortably has enough |
| Internet | Not required. Nothing about recovery uses it and there is not even an update check — unplug the network and everything works the same. The only traffic is an anonymous count: one line when the installer finishes, and one line each time the app is opened, which a switch in the window turns off |
There is no macOS or Linux build. A disk taken out of a Mac or a Linux machine can often still be recovered on Windows using Unlost — ext2, ext3, ext4 and XFS are read, and APFS and HFS+ are not.
Administrator rights, and why they are unavoidable
A deleted file has no directory entry any more, so there is nothing to open by name. The only way to find it is to read the volume the way the disk stores it, sector by sector, past the file system's own bookkeeping. Windows treats that as a privileged operation and will not grant it to an ordinary user process. That is why Unlost triggers one UAC prompt when it starts.
Any recovery tool that reads raw volumes needs this. One that claims it does not is either not reading raw volumes or not telling you the truth.
The elevation is used for exactly one thing: opening the volume for reading. Unlost installs no driver, registers no service, adds nothing to startup, changes no system or security settings, and does not stay resident after you close it. It uninstalls from Windows Settings like any other app. The security page goes through that in more detail.
Disk space
- To install: the installer is 4.0 MB. Install it on a drive other than the one you lost files from — installing onto the damaged drive can write over the files you are trying to get back. If the files were on your computer's own system drive, install to a spare USB stick.
- To recover: free space on the destination drive at least equal to the total size of the files you select. Unlost re-reads the destination's free space at the moment you press recover, adds up the files themselves rather than trusting a number from the interface, and refuses to start if it will not fit — rather than filling a disk and stopping halfway.
- To scan: nothing. A scan writes nothing anywhere.
- To image a failing drive: room for the whole drive. A 1 TB disk needs 1 TB, even if only a fraction of it holds data — an image is a copy of the medium, not of the files.
Drives and media you can scan
| Media | Notes |
|---|---|
| SD, microSD and CF cards | The best case in file recovery. Cards do not receive TRIM in normal use, so deleted files stay readable until something writes over them |
| USB flash drives | Same as cards |
| External hard drives | Fully supported, including drives with no readable partition table |
| Internal hard drives | Fully supported |
| Internal SSDs (SATA, NVMe) | Readable, but usually with nothing to find. Windows sends TRIM to internal SSDs, and the drive erases freed blocks on its own within seconds to minutes — after which those addresses read back as zeros for everyone. Why deleted files can be recovered, and when they can't explains this properly |
| External SSDs over USB | Depends on the enclosure — some pass TRIM through, some do not. A scan will tell you, because a TRIMmed area reads back as zeros |
| Whole physical disks | Scanned directly, which is what you want when Windows shows no drive letter, unallocated space, or "disk not initialized" |
| NAS disks | Take the disk out and connect it to the PC. ext2/3/4, XFS and Linux LVM are read; btrfs and ZFS are recognised and not read |
| Disk images | An image Unlost made, or a plain sector-by-sector .img, is scanned exactly like a drive |
| Phones and tablets over USB | Not scannable. A phone connected by USB presents itself as a media device rather than a drive, so there is no volume to read sector by sector. A memory card taken out of a phone or camera and put in a card reader is a different matter, and works normally |
| Optical discs, tape | Not supported |
| BitLocker-encrypted volumes | Identified, not decrypted. Unlost reports the encryption method, the unlock methods and the recovery key identifier so you know which of your saved keys is the right one |
The full list of file systems, partition layouts and file types is on what Unlost can read.
How long a scan takes
Roughly three minutes for a 32 GB memory card, and 40 to 90 minutes for a 1 TB hard drive. Files appear in the list as they are found, so you can preview and recover them while the scan is still running, and stopping is honoured within a fraction of a second rather than at the end of the current pass.
The deep pass is different: it reads every byte of the medium, which on a large disk is hours rather than minutes. It runs on its own when the file table gave nothing recoverable, and otherwise it is offered rather than started, because it returns files without names — worth an afternoon to somebody who has not found what they came for, and a waste of one to somebody who has.
A drive with a hardware fault is the exception to all of this. If a drive is clicking, stalling or disappearing and coming back, do not scan it: copy it first. A scan seeks all over a disk for hours, and a failing drive has a limited number of reads left in it.
Questions
Is there a portable version that does not need installing?
No. Unlost is distributed as a 4.0 MB installer and nothing else. The important part is where you install it: any drive except the one you are recovering from.
How do I remove it?
Windows Settings, Apps, Unlost, Uninstall — the ordinary way. Nothing is left running, no service is registered and no driver is installed, so there is nothing to clean up by hand afterwards.
Can I run it without administrator rights?
It will start, but it cannot open a drive for raw reading, which is the only thing it does. If you decline the prompt, close Unlost, right-click it, choose "Run as administrator" and scan again.
Windows warned me about the installer. Is that expected?
Yes, and it is worth understanding rather than clicking through. The installer is signed, but Unlost is new and Microsoft Defender SmartScreen has no reputation record for it yet, so the warning still appears — it is about how many people have run this exact file, not about what the file does. Windows will also name the publisher, Kanon Agro B.V., which is the company that publishes Unlost. The security page explains the warning in full, says who signed the file, and gives five ways to check the installer yourself before you run it.
Unlost is a Windows application. This download is a Windows installer, and it won't run on the device you're reading this on.
Free · Windows 10 and 11, 64-bit · 4.0 MB installer · install it on a drive other than the one you lost files from