I have an external USB drive which I share between my Linux laptop and my Windows work PC. I know that for Linux filesystems there's generally no need to defragment, but does this also hold true for Windows filesystems when used under Linux? Or does the Linux implementation of fat32 also fragment the data? If so, is there a tool I can use to defragment a fat32 partition?

I have searched for info on this, but all I seem to be able to find are threads about needing to defragment Linux paritions (ext2/3, reiserfs etc.), but nothing on fat32.

Any thoughts welcome.

I can't speak for the Linux implementation of fat32, but one straight forward thing you could try is to run the Windows defragmentation tool when you're using your USB drive on your Windows work PC. That should at least tell you how fragmented Windows thinks your drive is, and then you can decide whether or not to proceed with a Windows defrag.

After I'd posted, I realised I could just have done that! It reports that it is fragmented and that I should defragment it. I'm still curious is this is an inherent problem with fat32, or if this is just the way it's been implemented...

M$Windows uses the FAT32 partition differently than Unix or Linux uses the EXT3 <or other great File Systems>. Because it is written the way they are committed to writing it,..the results are also confined to the restrictions of the Operating System. As a model, two trains on separate tracks. Train A, perceives Unix instructions and has access permissions to avoid accidents. Train B has limitations to its code and must, respond to its commands without complete freedom to prevent accidents. Truly sad for the free world.