Windows refuses to copy a large file (video, ISO disc image, backup, virtual machine disk) to a USB flash drive, an SD card or an external drive, even though the free space shown is more than enough? In the vast majority of cases, the cause is not the available space but the drive's file system: FAT32 cannot hold a single file of 4 GiB or more. This guide helps you check this, then choose between formatting the drive (which erases its contents) and converting it without losing files, based on Microsoft's documentation.
Problem
- Copying a large file stops immediately with a message saying the file is too large for the destination file system.
- The destination drive still shows several gigabytes of free space.
- Small files copy normally to the same drive.
- The problem often affects a new USB flash drive or SD card, formatted as FAT32 by default.
Message shown by Windows (English version):
The file is too large for the destination file system.
Observe before acting
| Observation | Most likely cause | Step |
|---|---|---|
| "Too large" message with a file of 4 GiB or more | Drive formatted as FAT32 | Steps 1 and 2 |
| Message saying the disk is write-protected | Write protection, not a size limit | USB drive write-protected on Windows (French guide) |
| The drive does not appear in File Explorer | Detection problem | USB flash drive or external hard drive not recognised (French guide) |
| Message about a lack of space with several small files | The drive is really full | Free up space or use a larger drive |
Step 1: check the file system and the file size
When to use it: always, before formatting or converting anything.
According to the comparison table published by Microsoft, the maximum file size is 4 GiB on FAT32, compared with 2^64–1 bytes on exFAT and NTFS. A FAT32 drive can therefore hold dozens of gigabytes in total, but no single file of 4 GiB or more.
Suggested solution
- Open File Explorer, then This PC.
- Right-click the USB drive or disk concerned, then select Properties.
- On the General tab, read the File system line: FAT32, exFAT or NTFS.
- Right-click the file you want to copy, then Properties, and note its Size.
- For a command-line check, open Windows PowerShell and type the following command, replacing E with the drive letter. It only displays information and changes nothing:
Get-Volume -DriveLetter E | Select-Object DriveLetter, FileSystemType, Size, SizeRemaining
Expected result: if the file system is FAT32 and the file is 4 GiB or larger, you have found the cause. If the drive is already exFAT or NTFS, the size limit is not the cause: reply in this topic with the exact message.
Step 2: choose the right solution
| Situation | Suitable solution | Are the drive's contents kept? |
|---|---|---|
| The drive is empty or its contents are backed up elsewhere | Format as exFAT or NTFS (step 3) | No, everything is erased |
| The drive holds files you need to keep and will mainly be used with Windows | Convert to NTFS (step 4) | Yes |
| The destination device (TV, console, car stereo, camera) only accepts FAT32 | Keep FAT32 and copy files smaller than 4 GiB | Yes |
Before choosing, check in the manual of the device that will read the drive which file systems it accepts. According to Microsoft's table, NTFS supports permissions (access control lists), metadata journaling, encryption and compression, which exFAT does not. For a drive shared between several devices, exFAT is often the simplest choice, provided those devices support it.
Step 3: format the drive as exFAT or NTFS
When to use it: the drive holds nothing important, or its contents are already copied elsewhere.
Formatting erases all the contents of the drive. If the drive holds a bootable installer (for example a Windows installation drive), it will no longer be bootable and will have to be recreated.
Suggested solution
- Copy to the PC all the files on the drive that you want to keep.
- In This PC, right-click the drive, then select Format.
- In File system, choose exFAT or NTFS instead of FAT32.
- Leave the allocation unit size at its default, keep Quick Format ticked and give the volume a name if you wish.
- Click Start, confirm the warning, then copy your files and the large file back.
You can also format from the command line, from a Command Prompt opened as administrator (the format command requires membership of the Administrators group to format a hard drive). Check the drive letter twice: the command erases the volume you specify. Example to format E: as exFAT with a quick format and the label CLE:
format E: /FS:exFAT /Q /V:CLE
Replace exFAT with NTFS if you chose NTFS.
Expected result: the File system line in the drive's properties shows exFAT or NTFS, and the file larger than 4 GiB copies without an error message.
Step 4: convert to NTFS without erasing files
When to use it: the drive holds files you cannot move elsewhere, and it will mainly be used with Windows PCs.
Microsoft documents the convert command, which turns a FAT or FAT32 volume into NTFS while keeping existing files and folders intact. Two important precautions appear in this documentation:
- The conversion is one-way: a volume converted to NTFS cannot be converted back to FAT or FAT32. To go back, you will have to format it.
- A converted volume may perform less well than a volume formatted directly as NTFS, because the file table (MFT) is created in a different location.
Suggested solution
- Even though the conversion keeps the files, back up the important ones first: a power cut or removing the drive during the operation could damage them.
- Close all files and windows opened from this drive.
- Open Command Prompt as administrator (type "cmd" in search, then Run as administrator).
- Type the following command, replacing E: with the drive letter (the /v parameter shows the details of the operations):
convert E: /fs:ntfs /v
- If the command says it cannot lock the drive, close the programs using it and try again. Do not remove the drive before the operation has finished.
Expected result: the drive's properties show NTFS, your existing files are still there and the large file copies.
Special cases
| Situation | What to do |
|---|---|
| The destination device only reads FAT32 | Keep FAT32: only files smaller than 4 GiB can be copied to it. Check the device's manual to see whether it accepts exFAT or NTFS. |
| The drive must also be read by another system (Mac, Linux, console) | Check in that device's or system's documentation that it supports the chosen file system before formatting. |
| Windows or other operating system installation drive | Do not format it to store a large file: use another drive. |
| SD card from a camera or phone | Preferably format it from the device that uses it, following its manual, after copying its contents. See also SD card reader not recognised on Windows (French guide). |
Final check
- ☐ The drive's properties show exFAT or NTFS.
- ☐ The file larger than 4 GiB copies completely, without an error message.
- ☐ Your existing files are still there (conversion) or have been copied back (formatting).
- ☐ The device that needs to read the drive (TV, console, other PC) still recognises it.
Sources
- Microsoft Learn: File System Functionality Comparison (maximum file size, security, journaling)
- Microsoft Learn: format command
- Microsoft Learn: convert command (FAT/FAT32 to NTFS))
- Microsoft Learn: Get-Volume
Still having the problem?
Reply in this topic with your Windows version (Windows + R keys, then winver), the type and capacity of the drive (USB flash drive, SD card, external drive), the file system shown in its properties, the size of the file to copy and the exact message shown by Windows.