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Why Does My USB Drive Say It’s Full When It’s Not?

Mac book with code on the screen.

USB flash devices are normally very reliable, but they can occasionally have problems. Sometimes it’s an issue with the USB ports not working; other times your computer doesn’t recognize your drive. But one of the most common issues (and the easiest one to fix) is when your USB drive reads as full when you know it’s not.

You may notice this issue when you try to copy over some files onto your drive and you get the “File is too large for destination” error message. It may prompt you to delete excess files to make room. But how can that be? You were sure there was plenty of room.

If you’re absolutely sure you have adequate space on your flash drive (you can see how much is available when you look at your drive in My Computer or by clicking the drive in Mac and checking under “Get Info” beneath “File”), then the problem is a either formatting, hidden files, user error, or over-provisioning.

Formatting to Restore to Full Capacity

The issue could be due to the pre-formatted file system on your drive which may have a file transfer limit below the amount of data you’re attempting to copy or transfer.  For example, the FAT32 file system has a file size limit of 4GB. This means that, regardless of how empty your drive is or how much storage capacity it has, you won’t ever be able to transfer 4GB or more at once. You could break up your data into chunks but that’s inefficient and annoying.

The solution is simply to reformat your drive so that it can handle the large data job. It’s very simple DIY solution that doesn’t require buying any additional software. Check out our blog on how to reformat a USB drive yourself; we also give you a quick run through on the different file formats. We recommend using the exFAT system as it has a high compatibility with large file sizes and is lightweight, without the mess that comes with the NTFS system.

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Hidden Files

If formatting isn’t the issue, then likely your drive isn’t as empty as you think. This is because, even on a brand-new flash drive, it is not exactly empty. In fact, no USB drive is completely empty upon purchase. “Blank” drives still contain hidden folders. These might be:

  •          .fseventsd
  •          .Spotlight-V100
  •          .Trashes

These are typically part of initial formatting of your drive and are found at the root level. These folders are placed on an empty drive to help your computer communicate with your flash drive. The “.Spotlight-V100” and “.fsventsd” files contain meta data (or data about data) that helps the indexing of files you store on your drive. These aren’t causing your USB to read as full but the “.Trashes” folder is. Note that this file is only found on Mac operating systems. You won’t find it on other systems. If you delete files using a Windows computer, for example, and then plug it in a Mac, it will generate the .trashes folder.  

When it comes to taking out the trash, flash drives are a lot like computers: deleting something doesn’t automatically make it go away. This is the number one reason why USB drives read as full—your flash memory is being used up by your deleted data!

When you delete a file on a hard drive, it gets sent to a waiting area where it can either be restored or permanently deleted. Flash drives work the same way: that’s what the “.Trashes” hidden folder is for. There is one crucial difference, however, between how hard drives and flash drives take out the trash: there’s no “empty trash” function inside your USB.

The only way to free up that used up storage space is to permanently delete your trashed files. To do that, though, you’re going to need a little help from your computer.

How to Delete .Trashes Using Terminal on Mac

  1.       Plug in your drive
  2.       Open your Applications folder, select Utilities, and then double click on Terminal
  3.       Type: “sudo rm -R” and then press your spacebar ONCE; there needs to be a space after the “R”
  4.       Control click your trash icon to open
  5.       Select files in your trash
  6.       Drag to the Terminal window
  7.       Press Enter
  8.       Enter your administrator password
  9.       Press Enter

How to Delete USB Drive Files on Windows/PC

  1.       Plug in your drive
  2.       Open your drive using File Explorer
  3.       Select the existing files you want to delete
  4.       Right click, and then select “Delete”
  5.       Open up your Recycle Bin on your Desktop, right click on an empty space, and choose “Empty Recycle Bin”

As previously mentioned, the “.Trashes” folder only exists on Mac systems but you should still get in the habit of properly deleting files from your USB drive on Windows/PC systems. They could be clogging up your storage space.

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A Quick Note about GiB vs GB…

A possible explanation for why you don’t have as much room on your USB drive as you thought could boil down to simple user error.

As you probably know, digital information is measured in bytes. You’ve probably seen GiB and GB thrown around a lot, but you need to be aware of the difference. They’re pretty closely related but a gibibyte (GiB) is slightly bigger than a Gigabyte; 1 GiB is roughly equal to 1.074 GB. Why is this important? After all, you’ve never seen a flash drive with GiB on it, have you?

Well, not your flash drive but your computer and other software can display the two incorrectly, or at least in a confusing way. For example, if you have a drive that says 500GB, your computer may display it as only 465GiB! Since the GiB is a little bigger, it actually ends up translating up to the same amount of bytes but our eyes sort of glaze over the “i” in GiB and assume we’re reading GB.

Over Provisioning

One other possibility is a practice called “over provisioning” which is the practice of reserving a small amount of storage space to devote to memory controller functions. Over provisioning can help make a device more efficient by allocating resources to controller performance but this means that a small degree of advertised storage capacity is taken up. This practice is industry standard for SSDs (solid state drives) but you might see it in higher quality USB drives. If your drive is designed to utilize over provisioning, then there isn’t much you can do about it. You’ll just have to accept you have slightly less space than you thought.

A Quick Note about GiB vs GB…

A possible explanation for why you don’t have as much room on your USB drive as you thought could boil down to simple user error.

As you probably know, digital information is measured in bytes. You’ve probably seen GiB and GB thrown around a lot, but you need to be aware of the difference. They’re pretty closely related but a gibibyte (GiB) is slightly bigger than a Gigabyte; 1 GiB is roughly equal to 1.074 GB. Why is this important? After all, you’ve never seen a flash drive with GiB on it, have you?

Well, not your flash drive but your computer and other software can display the two incorrectly, or at least in a confusing way. For example, if you have a drive that says 500GB, your computer may display it as only 465GiB! Since the GiB is a little bigger, it actually ends up translating up to the same amount of bytes but our eyes sort of glaze over the “i” in GiB and assume we’re reading GB.