I connected an 1 TB Toshiba external HDD previously used on windows pc to my new MacBook Air and a message popped up for if I wanted to use this drive for time machine backup and since this is the first time i'm using mac I clicked "later". I think it got formatted so I tried some data recovery softwares but was unable to recover any data. I had lot of data on it which I would like to recover, is it possible?

  • It was probably an NTFS formatted drive. Mac can read but not write to NTFS by default [but can be tweaked to do so], so if it did anything at all, it would have changed the format to HFS+. Your best bet right now would be to attempt to recover your data from a Windows machine
    – Tetsujin
    Oct 17 '14 at 9:16
  • You are probably right. It was an NTFS formatted drive and Mac has converted it to HFS+ in order to use it with time machine. Right now it is showing empty on Mac as well as pc. Do you think the data is still there? I didn't write anything on it yet.
    – Melvin
    Oct 17 '14 at 9:27
  • So long as Time Machine hasn't started to write to it, the chances are that under the new format, all the data is still there. You will need a good Windows recovery tool to get at it, though. It can be done on Mac, but as you're new to Mac & presumably currently more comfortable with Win, that's probably easiest for now. I'm not great on Win, but maybe one of these? lifehacker.com/5237503/five-best-free-data-recovery-tools
    – Tetsujin
    Oct 17 '14 at 9:30
  • I would prefer to do it on win but do these softwares read HFS+ formatted drives?
    – Melvin
    Oct 17 '14 at 9:45
  • They wouldn't need to, as there's 'nothing in' that partition. They need to figure out or be told that they should be looking for an old NTFS partition & scavenge that. Whether they can still get file names is doubtful, probably just raw data
    – Tetsujin
    Oct 17 '14 at 9:58

To recover data from an external HDD formatted by Mac, you can use software TestDisk. Formatting is mainly performed when the HD gets corrupted due to software conflicts, bad sector etc. In Mac OS X, you can use ‘Disk Utility’ to perform the formatting process. Once formatting is completed, you can use advanced data recovery tool.


Seconding Douglas Gordon's answer, I've had a lot of success recovering data with TestDisk in the past.

However if you are less comfortable using a command line tool, I would recommend Data Rescue as well. You could start with the free option (which allows recovery of up to 2GB of data) to see whether it will actually work for you. They even list your specific situation ("accidentally reformatted hard drive") as one of their use cases.

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