Safely Remove Hardware

How is a usb stick supposed to react if you unplug it while it was trying to write something?

The standard "interchange" filesystem on USB sticks that everything can understand is still FAT.

FAT is not a journalling filesystem -- you can still corrupt the thing if you interrupt use of a mounted drive.

Plus, even if you have a journaling filesystem, it's probably good practice to unmount because even though you won't corrupt the filesystem, it still might be that data won't have been written to said drive -- like, if you save a new version of the file, you might have the old version of the file.

It could be that OSes have tried to be more aggressive in buffer management, tried to flush dirty data to USB flash drives or something sooner to help shrink the size of the window in time where issues can come up. But I still wouldn't just go running around yanking USB flash drives out of machines without unmounting them -- that's the only situation for which you can be guaranteed no issues.

EDIT: Honestly, I think that it's a little disappointing that it's the case that we don't handle this well in 2025. Apple handled removable media on Macs with 3.5 inch disks correctly by having the user ask the OS to do the eject, which physically ensure an unmounted disk prior to eject. They did have a pinhole for an "emergency" eject, but the normal case was for a clean unmount. DOS and Windows used a mechanical eject button, which was still liable to see issues.

checks Zip drives

It looks like Zip drives had a software eject button, so they'd also be able to ensure an unmount.

CD-RW drives have a software eject button -- the OS tells the drive to lock the tray prior to beginning a burn -- so they were okay too.

I'd guess, though I don't have experience, that tape drives probably all ensure a clean unmount.

But USB flash drives, probably the most common form of transportable writeable media in 2024, don't, which is a little disappointing.

I've bombed a couple in the last few years since they didn't have an indicator light, and I was in a rush.

Only on Windows as far as I'm aware.

Linux and MacOS still struggle with it.