The honest answer first: no free tool repairs a physically failing USB drive. What free tools can do is diagnose the problem, test whether the capacity is real, fix a file-system error, or wipe and repartition a drive that is otherwise healthy. If your drive has a dead controller, worn-out flash, or a fake capacity, the reliable fix is replacement, not another formatting attempt. This page compares the free tools people actually reach for, states each one’s limit, and gives a safe order to try them in.
Start with diagnosis, not repair. Running a formatter on a drive you have not identified yet can destroy the evidence you need and, worse, can make a failing drive look healthy for just long enough to lose data on it. Identify the drive first with ChipGenius from our download page, then choose the tool that matches the diagnosed problem. The comparisons below follow that order.
ChipGenius: diagnose before you touch anything
ChipGenius is a portable Windows diagnostic that reports the controller, vendor and product IDs, and flash identification for a USB flash drive. It does not repair, format, test capacity, or recover files. Its value in a repair workflow is that it tells you whether the drive is even identifying itself correctly. If ChipGenius shows a plausible controller and flash, you have a drive worth testing further. If it shows nothing on multiple computers and ports, you likely have a hardware failure that no software tool will fix. For the version choice, see ChipGenius v4.21 vs v4.19, and for the wider tool landscape, see ChipGenius vs alternatives.
H2testw and FakeFlashTest: prove the capacity is real
H2testw writes test data across the whole drive and reads it back. It is the standard free way to prove a drive’s usable capacity, and it is the tool to run when a drive claims a large size for a suspiciously low price or when files disappear after the drive fills past a certain point. It is slow on large drives, it fills the drive with test data, and it does not repair anything: a failed result means the drive cannot be trusted at its labelled size. FakeFlashTest is a faster first check that can flag many fake drives without a full pass, but a full H2testw run is the stronger proof before you trust a drive with important data.
A common mistake is to “fix” a failed capacity test by formatting. Formatting does not create real flash memory. At most, you can repartition a fake drive down to its tested real capacity and use only that portion, and even that is a stopgap for non-critical files. For anything important, replace the drive. A verified replacement flash drive such as the Samsung BAR Plus or the SanDisk Ultra Fit, or a portable SSD such as the Samsung T7 for larger backups, is the honest next step; see portable SSD vs USB flash drive to choose between them.
CHKDSK: file-system errors only
CHKDSK is the Windows command-line checker for file-system errors. It can fix a corrupted file system, recover readable information from bad sectors where possible, and make a logically damaged volume usable again. It cannot fix a failing controller, cannot restore worn flash, and cannot turn a fake drive into a genuine one. Run it only after you have backed up whatever you can still read, and only on a drive whose capacity has already been verified or is not in doubt. If CHKDSK reports many bad sectors or the drive disconnects during the scan, stop and replace the drive instead of running it repeatedly.
Disk Management and diskpart: partitioning, with a warning
Windows Disk Management can delete, create, and format partitions on a drive that Windows detects. Diskpart can go further: its clean command removes the partition table when Disk Management cannot, which sometimes rescues a drive whose partitions are corrupted. Both tools erase data, and diskpart in particular gives no second chance if you pick the wrong disk number. Before any clean or format, confirm the disk number, confirm you have a backup, and confirm the drive passed a capacity check. If the drive is not detected in Disk Management at all, neither tool can help, and the problem is hardware.
SD Card Formatter: the right formatter for cards
SD Card Formatter formats SD and microSD cards to the SD specification and is the right choice for camera cards that misbehave after a generic format. It is not a USB flash drive repair tool, it does not diagnose controllers, and it does not test capacity. Use it for cards, in a card reader, after you have backed up the card’s contents. A reader such as the Anker card reader is a practical accessory for that job, and a replacement card such as a Samsung microSD card is the fallback if the old card keeps failing after a proper format.
| Tool | Fixes | Does not fix |
|---|---|---|
| ChipGenius | Nothing directly; identifies the hardware | Capacity, file system, controller, or flash failure |
| H2testw / FakeFlashTest | Nothing directly; proves real capacity | Fake capacity, worn flash, dead controller |
| CHKDSK | File-system errors on a working drive | Hardware failure, fake capacity |
| Disk Management / diskpart | Partition and format problems on a detected drive | Undetected drives, fake capacity, worn flash |
| SD Card Formatter | Card formatting to SD spec | USB stick diagnosis, capacity, hardware failure |
What about file recovery?
If the drive is detected and the problem is deleted or formatted files rather than hardware failure, file-recovery software is a separate category from repair tools. The official pages for R-Studio and DMDE are linked here for readers who want to evaluate recovery options; no commission is claimed for those links, and recovery software cannot rescue files from a drive whose controller is dead or whose flash is unreadable. Stop using a drive you need to recover from, because every write risks overwriting the very files you want back.
A safe order to try
- Back up anything you can still read, before any test or repair step.
- Identify the drive with ChipGenius on a known-good port and computer.
- If capacity is in doubt, run a capacity test and believe a failed result.
- If the file system is corrupt on an otherwise verified drive, try CHKDSK.
- If partitions are corrupt on a detected drive, try Disk Management, then diskpart only with the disk number double-checked.
- If it is a camera card, format it with SD Card Formatter rather than a generic formatter.
- If the drive is undetected, disconnects, or fails testing, replace it and verify the replacement before use.
That order saves time because it prevents the most common waste in USB repair: formatting first and diagnosing never. A drive that survives diagnosis, capacity testing, and a clean format on a verified workflow is worth keeping. A drive that fails any of those steps is not a repair project; it is a replacement waiting to happen. Disclosure: some links on this site are affiliate links; see our affiliate disclosure.