Free Data Recovery Software: What It Can and Cannot Do

Searching for free data recovery software returns hundreds of products, and most of them are free only up to a point. That is not a trick in itself: writing software that reads damaged file systems correctly is specialist work. What matters is knowing which kind of free you are looking at before you run it on the only copy of your files.

Fully free tools exist, some of them open source. They are often capable on simple cases, such as recently deleted files on a healthy drive, but tend to have plain interfaces, limited file-system support and no one to ask when a result looks wrong.

Free editions with a limit let you save a fixed amount, commonly between 500 MB and 2 GB, and ask for payment above that. They suit one lost document or a handful of photos. They do not suit a formatted drive.

Free scan and preview is the third kind. The software runs every scan without a time limit and shows the files it found, with previews, and a licence is needed only to save them. AS Data Recovery works this way: the free edition runs the quick and deep scans and previews every file, and saving requires a Professional or Enterprise licence. The advantage is that you pay only after you have seen your own files listed as recoverable.

On a drive that Windows detects and can read, recovery software can list deleted files that the file system still records, find lost or deleted partitions, bring back files from before a quick format, and find photos, videos and documents by their content when no name is left. Whether a particular file comes back intact depends on one thing: whether its space on the drive has been reused since it was lost.

No software can read a drive the computer does not detect, or one with a mechanical, firmware or electronics fault. No software can return data that has been overwritten, or data on an SSD after TRIM has erased the freed blocks. And no software can decrypt files encrypted by ransomware without the key, although large files such as databases and virtual disks are often only partly encrypted, which is a different kind of recovery.

A product that promises to recover everything from any drive is describing something that does not exist.

Do not install the software on the drive you want to recover from: installing writes data, and that data can land on your lost files. Scan the drive from another computer or from a different system drive. Run the quick scan first, since it takes minutes. Use the preview: a photo that displays or a document that opens in preview will open after recovery. Check whether the software grades deleted files as intact or overwritten, and trust that grading more than the file count.

If the scan shows your files as intact, recover them to a different drive. If it shows them as overwritten, or does not find them after a deep scan, another program will not change the result, because all of them read the same drive.

Stop if the drive makes unusual noises, disappears while scanning, or the scan slows to a crawl with read errors. Those are signs of a failing drive, and continued scanning can finish it off. The safe order is to image the drive first and scan the image, and with a badly failing drive that imaging is lab work.