I have Mac OS 8 in Polish (from FTP). After extracting I got a strange IMG file.
I tried to open it in TransMac, which opens many MacOS CD images well (Mac OS 8 English installation ISOs too), but no success - CD shows in list, but no files or filesystem. Trying to burn it hangs the program.
Tried to boot Basilisk II from it - no success.
Tried to open it with Apple Disk Utility (Mac OS X 10.5 on Power Mac G4) - I can't mount, open, convert or burn it on my Mac because of "not recognized" error.
Burning it blindly using UltraISO makes disc unusable, none of my Macs can read/boot from it.

How to record it? Is it a CD image at all?

Assuming the disc image isn't corrupt, just change the file extension from .img to .iso and burn to disc. And yes, IMG is a disc image file format, but there are several different encoding standards (I think that's the term?) for it, some of which can only be read by specific programs.

Thanks for reply.
I think my IMG is some specific format, made with unknown software.
Any chance of identifying it?
Most Apple CD images start with some amount of zeros. This file starts with more (~150K) of 00 00 7F 00 00 7F pattern. Usually Apple table should come - here unknown (compressed?, encrypted?) data starts, runs to about 250K and goes back to 00 00 7F pattern to ~400K. Now something like the actual data starts, but filled with "streaks" of 00 00 7f pattern in random places and random length.

It's been years since I've had to deal with the IMG format at any sort of low level, but I believe the IMG file format allows for certain functionality beyond a simple ISO. If memory serves, your suggestion of compression or encryption are both possibilities as I believe IMG allows (allowed?) for both.

Your best bet is to try burning the image on a legacy Mac running 9.x and see if that brings you any success. The second best option is to fire up an already existing OS9 machine in SheepShaver and try to mount in that VM. (Note: some legacy IMG files will refuse to mount in any semi-modern version of OSX (10.6+) so failure on that front doesn't necessarily mean that the IMG isn't intact.)

.img files are disk images, but these are the New Disk Image Format files created by DiskCopy. You should be able to mount it using Toast 5.2.3 in Mac OS 9 and then burn it to a CD.

Or, if you're running anything before Mac OS X 10.6, you should be able to use Disk Utility to Convert the .img file to .cdr or .dmg and burn it to a CD.

You can use fileinfo.com and it will give you a list of all the programs that can

Out of curiosity, have you tried extracting it using something such as 7-zip?
I find 7-zip works with most things unless they're encrypted or corrupted .