What Is an SFCACHE File Used For?

This is a ReadyBoost virtual RAM file

What to Know

  • An SFCACHE file is a ReadyBoost cache file.
  • It's used as virtual memory on removable devices in some Windows versions.

This article describes what an SFCACHE file is and how it's used by Windows, plus how it's different from CACHE files.

What Is an SFCACHE File?

A file with the SFCACHE file extension is a ReadyBoost cache file that's created on a compatible USB device, like a flash drive or SD card, that Windows can use for extra memory. It's normally called ReadyBoost.sfcache.

ReadyBoost is a feature first introduced in Windows Vista, where the operating system improves system performance by dedicating unused hardware space as virtual RAM—the SFCACHE file holds the data stored in this virtual RAM space.

USB flash drive and multiple USB port malfunctions

kyoshino / E+ / Getty Images

While physical RAM is the fastest way to access data, using flash memory is even faster than accessing the same data on a hard drive, which is the whole idea behind ReadyBoost.

How to Open an SFCACHE File

SFCACHE files are part of the ReadyBoost feature and should not be opened, deleted, or moved. If you'd like to remove the SFCACHE file, disable ReadyBoost on the drive.

You can delete the ReadyBoost cache file from a USB device by disabling ReadyBoost. Right-click (or tap-and-hold) the device and choose Properties. In the ReadyBoost tab, select Do not use this device.

Screenshot of the ReadyBoost settings on a USB drive

It's a good bet that the only use for SFCACHE files is with ReadyBoost, meaning there's never a need to open the file. However, if your file doesn't seem to have anything to do with ReadyBoost, try using a free text editor to open it as a text file. You might find some text there that can help you identify what program was used to build that specific SFCACHE file.

Enabling ReadyBoost

If you're looking to enable ReadyBoost, you can do that, too, from the same place—you have the option to use the entire device for virtual RAM or just a section of it.

Not all devices are fast enough to support ReadyBoost. You'll know this if when attempting to set it up, you see a This device cannot be used for ReadyBoost message.

If you want to use SFCACHE on your device, make sure it has:

  • A total storage capacity of at least 256 MB
  • At least 64 KB of free space available
  • An access time of 1 ms or less
  • At least a 2.5 MB/s throughput for 4 KB read access
  • At least a 1.75 MB/s throughput for 1 MB write access


SFCACHE files are similar to CACHE files—they're both used to store temporary data for the purpose of repeated access and improved performance.

However, CACHE files are more of a general name and file extension for temporary files used in lots of different software programs, which is why it's safe to clear them out.

SFCACHE files are reserved for a different purpose, acting more like physical RAM, and used solely with the ReadyBoost feature in Windows operating systems.

How to Convert an SFCACHE File

Most files can be converted to other formats using a free file converter, but that's not the case for SFCACHE files. Since they are used only as a repository for files, you can't convert them to any other format.

If your file has nothing at all to do with a ReadyBoost SFCACHE file, but you do know what program is used to open it, try looking for an Export menu or an option under the File > Save As menu, for saving the file to a different format.

More Help With SFCACHE Files & ReadyBoost

The sfc command is in no way related to SFCACHE files, so if you're dealing with the System File Checker in Windows, it has nothing to do with ReadyBoost.

Similarly, even though "sfc" is used in both, files that end with .SFC have nothing to do with .SFCACHE files but are instead used by SuperNintendo ROM files, Motic Microscope images, and Creatures saved game files.

  • Is NTFS or FAT32 the better file system for ReadyBoost?

    NTFS (New Technology File System) is the newer of the two and the default file system for Windows. FAT32 is the most recent version of the File Allocation Table (FAT) system and is typically the default format for flash drives. However, FAT32 limits the ReadyBoost cache size to 4GB, whereas NTFS doesn't.

  • How do I enable ReadyBoost in Windows 10?

    To enable ReadyBoost in Windows 10, insert your flash drive and select Speed up my system from the AutoPlay dialog box. Select the ReadyBoost tab and choose Dedicate this device to ReadyBoost or Use this device and move the slider to adjust the amount of space to use for ReadyBoost. Select Apply > OK.

Was this page helpful?