Why Can’t I Copy Large Files to My High Capacity Flash Drive?

You have a brand new high-capacity flash drive that can store more than the hard drive of your first three computers combined, but when you go to copy a large file it denies you. What gives? Read on as we show you how to solve your flash drive frustrations.

Dear How-To Geek,

I recently purchased a 64GB USB 3.0 flash drive, plugged it into my computer, and started copying some files onto it I wanted to transfer to another computer. The little files (MP3s, documents, etc.) all transferred fine but I have some DVD ISO files on there and when it came time to copy them I got the error “The file ‘DVDBACKUP1’ is too large for the destination file system.” and the transfer fails.

What exactly does that error mean? Why can’t I put a 4.5GB file on a 64GB drive? Help!


Flash Drive Frustrated

We can certainly understand your frustration: here you were all ready to copy the files and then it just ground to a halt with a relatively cryptic message. Don’t worry though! We can not only solve the mystery of the stubborn file but show you how to fix it in the process.

First, let’s explain why you couldn’t copy it in the first place: the flash drive’s file system. A file system, which is a separate thing from an operating system and other mechanisms on a computer, is an organizational scheme used to control how data is stored and retrieved on a a given storage medium (like a hard disk, a DVD disc, or a removable flash drive). There are a multitude of file systems in the world that have features big and small that are useful (and even mission critical to the applications they are used in) such as native error checking and correction, journaling, permission schemes, and more.

RELATED: Why Do Removable Drives Still Use FAT32 Instead of NTFS?

Nearly every flash drive in the world ships formatted as with the FAT32 file system. FAT32 isn’t the most robust file system around but it has been around for ages, it is widely supported, and most of the time the applications one would use a flash drive for do not require the advanced features found in other file systems (and, in fact, some of those advanced features could even shorten the life of the drive via increased read/writes). If you’re curious as to why FAT32 is still so prevalent, check out our article HTG Explains: Why Are Removable Drives Still Using FAT32 Instead of NTFS?

Despite the ubiquitous nature of FAT32, however, it has one big shortcoming in the age of large files: the maximum possible file size for FAT32 files is 4GB. (If we’re being technical it’s actually 4GB minus a single byte or 4,294,967,295 bytes). These days 4GB isn’t exactly a whopper of a file and it’s real easy, as you discovered, to exceed the 4GB barrier with large video files, DVD and Blu-ray ISOs, and other large files.

Now that we know why you can’t copy that DVD ISO file over to your nice spacious 64GB flash drive, what can we do about it? Fortunately the fix is very simple. We’ll switch the file system to a file system which allows for larger-than-4GB file sizes.

We’ll demonstrate with a 16GB flash drive we have laying around. The flash drive is formatted in FAT32 and if we attempt to copy a 7.63GB ISO file, as seen in both the screenshot above and the header image for this article, we get the same error you got the file is “too large for the destination file system”.

To remedy that situation we’ll ensure there is no data on the flash drive that needs to be copied back to the machine or backed up and then we’ll format it to the NTFS file system (which allows for files ranging in size from 128GB to 256TB depending in the implementation used, more than enough for your needs).

We can swap out the file system by simply selecting the drive in Windows Explorer via right-click and then, in the right-click context menu, selecting “Format…”

In the Format menu, as seen above, change the file system from “FAT32” to “NTFS”. Leave the “Allocation unit size” at the default of 4096 bytes. Check “Quick Format”. Click “Start” to format the drive with a new file system.

Now that we’re sporting a large-file-friendly flash drive it’s time to transfer a large file and see what happens.

Success! Now that the flash drive is formatted to NTFS it has no issue accepting a 4+GB file size and we’re able to transfer that 7.63GB ISO with ease. Your super sized flash drive is now ready to accept super sized files.

Have a pressing tech question about storage, Windows, or any other computer problem under the sun? Shoot us an email with your question at ask@howtogeek.com and we’ll do our best to answer it.


Jason Fitzpatrick is a warranty-voiding DIYer who spends his days cracking opening cases and wrestling with code so you don't have to. If it can be modded, optimized, repurposed, or torn apart for fun he's interested (and probably already at the workbench taking it apart). You can follow him on if you'd like.