Many people have saved important files to their USB drive then tried to open them on another computer and had that sinking feeling when they’ve seen that the file isn’t there. It’s incredibly frustrating when this sort of thing happens, especially when it was the only copy. The problem is that most of the time, files do save to USB drives properly, so it can be easy to assume this is the case all the time.
The issue is really caused by a quality of life feature, called “Quick removal”. Historically with USB drives, you needed to manually click “Eject” for the USB drive to be able to safely remove the drive. This was because data wasn’t necessarily written to the USB drive when you thought it was. Instead, the operating system queued the data up to be sent to the USB drive when it was convenient. Clicking “Eject”, told the operating system that you wanted to remove the USB drive, so it prioritised ensuring that all the data was written to the drive before confirming that it was ready to be unplugged.
Of course, the clumsy user experience of having to click “Eject” and then wait for something that didn’t even automatically eject like a CD or DVD was generally not very popular. To make the user experience better, the “Quick removal” feature was added. “Quick removal”, specifically writes all data to the USB drive as soon as possible, leaving it in a state where it is ready to be removed as soon as the user wants, even without clicking “Eject”.
This means that generally, it’s safe to pull a USB drive out of the computer and assume your files will be saved on there correctly. Unfortunately, that’s not always the case. Larger files take longer to write to the USB stick, and if you assume it’s safe to remove before the file has finished being saved, then the file gets corrupted. Additionally, some programs wait to write certain data until the moment that the document is closed, meaning that if you pull the USB drive out after saving, but before closing, not everything is saved.
To be 100% sure that your files are properly saved to your USB device, you should always use the “Eject” or “Remove safely” option.