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exFAT facts for kids
| Developer(s) | Microsoft |
|---|---|
| Full name | Extensible File Allocation Table |
| Introduced | November 2006 with Windows Embedded CE 6.0 |
| Partition IDs |
|
| Structures | |
| Directory contents | Table |
| File allocation | bitmap, linked list |
| Bad blocks | Cluster tagging |
| Limits | |
| Max volume size | 128 PB, 512 TB recommended |
| Max file size | 128 PB |
| Max no. of files | up to 2,796,202 per directory |
| Max filename length | 255 characters |
| Allowed filename characters |
all Unicode characters except U+0000 (NUL) to U+001F (US) / (slash) \ (backslash) : (colon) * (asterisk) ? (question mark) " (quote) < (less than) > (greater than) and | (pipe)(encoding in UTF-16LE) |
| Features | |
| Dates recorded | Creation, last modified, last access |
| Date range | 1980-01-01 to 2107-12-31 |
| Date resolution |
|
| Forks | No |
| Attributes | Read-only, hidden, system, subdirectory, archive |
| File system permissions |
ACL (Windows CE 6 only) |
| Transparent compression |
No |
| Transparent encryption |
Yes, EFS supported in Windows 10 v1607 and Windows Server 2016 or later. |
| Other | |
| Supported operating systems |
|
exFAT stands for Extensible File Allocation Table. It is a special way that computers organize and store files on memory devices. Microsoft created exFAT in 2006. It works really well with flash memory devices like USB flash drives and SD cards.
Before 2019, exFAT was a secret technology owned by Microsoft. But then, Microsoft shared how it works. This made it easier for other companies to use exFAT in their products.
exFAT is useful when other file systems like NTFS are too complicated. It is also great when you need to store very large files, bigger than the 4 GB limit of older systems like FAT32.
The SD Association chose exFAT as the main file system for large SDXC and SDUC cards. These are memory cards bigger than 32 GB.
Contents
History of exFAT
exFAT first appeared in late 2006. It was part of Windows CE 6.0, a special Windows version for small devices. Later, regular Windows computers got exFAT support. This happened with Windows Vista Service Pack 1 and Windows Server 2008 in February 2008. An update also came out for older systems like Windows XP and Windows Server 2003.
Many companies that make small devices or media cards use exFAT. This is because exFAT is simple and doesn't need a lot of computer memory or power. It's easy to build into a device's basic software, called firmware.
What exFAT Can Do
exFAT has many cool features that make it better for modern storage.
Handling Large Files and Storage
One of the biggest improvements is how exFAT handles file sizes. It can store files up to 16 exabytes (that's a huge number!). This is much bigger than the 4 GB limit of older FAT32 systems. This means you can easily move very large files, like long HD videos, between Windows, Linux, and macOS computers.
exFAT can also manage very large storage devices. It can handle volumes up to 128 PB. This is a massive amount of storage, much more than the 2 TB limit of FAT32.
Managing Many Files
exFAT can hold a lot of files in one folder. You can have up to 2,796,202 files in a single directory. This is a big jump from older systems.
It also improves how quickly it finds free space and deletes files. This is thanks to a special "free-space bitmap" that keeps track of available space.
Time and Date Tracking
exFAT records when files are created or changed with great accuracy. It can track times down to 10 ms. It also records the last time a file was accessed, which older FAT systems didn't do as precisely.
Starting with Vista SP2, exFAT also records timestamps with a time zone marker. This helps keep times correct no matter where you are in the world.
Other Useful Features
- Permissions: exFAT can support access-control lists (ACLs). This means you can set specific permissions for who can read or change files, though this is mostly used in special Windows CE versions.
- Large Video Recording: Digital cameras often use exFAT. This allows them to record long HD videos without splitting them into smaller files. Older FAT32 systems would break videos into 2 or 4 GB chunks.
- Encryption: exFAT supports EFS in newer Windows versions. This helps keep your files secure.
Windows XP needs a special update (KB955704) to use exFAT. Windows Vista needs its SP1. Newer Windows versions like Windows 7 and 10 work well with exFAT. Windows 7 even lets you use exFAT drives for ReadyBoost, which helps your computer run faster.
How exFAT Works Efficiently
exFAT is designed to be fast, especially for flash memory cards like SDXC. It helps achieve quick write speeds by reducing how much work the file system has to do.
It uses a "cluster bitmap" to quickly see which parts of the storage are free or used. This is much faster than the older FAT table. Also, a special marker tells the exFAT driver if a file is stored in one continuous piece. If it is, the driver can read it much faster.
Where exFAT is Used
exFAT is supported by many operating systems:
- Windows XP (with an update) and later versions
- macOS (starting from 10.6.5)
- Linux (natively since kernel 5.4, or with FUSE)
- iPadOS and iOS (starting from 13.1)
- Android 13 and some older Android devices
- ChromeOS
- OpenHarmony and HarmonyOS NEXT
Many companies use exFAT in their products. This includes cameras, camcorders, digital photo frames, and even some TVs and media players. It's the official file system for SDXC cards. This means any device that wants to be called "SDXC compatible" must support exFAT.
Some USB drives and solid-state drives (SSDs) also come pre-formatted with exFAT. This helps them work with many different devices right away. Companies like Apple, Google, and Samsung have agreements to use exFAT.
Technical Details
exFAT uses some clever methods to manage files.
Finding Files Quickly
When you look for a file, exFAT uses a special "hash" (a short code) of the file name. It compares these short codes first, which is much faster than comparing the full names. If the codes match, it then checks the full name to make sure it found the right file. This makes searching for files very efficient.
Checking for Errors
exFAT includes ways to check if data has been corrupted. It uses "checksums" (like digital fingerprints) to make sure important parts of the file system are correct.
- It checks the "volume boot record," which helps your computer start up.
- It checks a table used for converting file names.
- It checks the information for each file, including its name, size, and location.
If any of these checks fail, it means something might be wrong. The file system might not load, or it might only load in a "read-only" mode to prevent further damage.
Optimizations for Flash Memory
exFAT has features designed specifically for flash memory, like those in USB drives and SD cards:
- It aligns file system structures to match the way flash memory stores data. This helps writes happen more efficiently.
- It avoids using a "journal," which is a log of changes. This means less data is written, which can help flash memory last longer.
| Boundary alignment (format) | OEM parameters (use) | TRIM (use) | Note | |
|---|---|---|---|---|
| Windows CE | Yes | Yes | Unknown | |
| Windows Desktop and Server | Yes | Yes | No | |
| Linux kernel | since 5.7 | ignored | since 5.13 | exfatprogs is assumed to be used for formatting. |
Other Ways exFAT is Used
Legal Status
For a long time, exFAT was a "proprietary" file system. This meant Microsoft owned the patents and you needed a license to use it. This made it hard for open-source projects (like Linux) to include exFAT support.
However, in August 2019, Microsoft changed this. They published the full details of exFAT and allowed members of the Open Invention Network (OIN) to use their patents. This was a big step, and it led to native exFAT support being added to the Linux kernel in version 5.4 in November 2019.
Different Implementations
There are several ways exFAT is used on different systems:
- FUSE-based: For FreeBSD, many Linux versions, and older Mac OS X, there's a system called fuse-exfat. It lets these systems read and write exFAT drives.
- Linux Kernel: Samsung Electronics created a direct Linux kernel driver for exFAT. This was added to the main Linux kernel in version 5.4 and improved in 5.7. It's used on many Linux and Android devices.
- Commercial Solutions: Companies like Paragon Software Group and Tuxera offer their own versions of exFAT support for Android, Linux, and other operating systems. These are often licensed from Microsoft.
- DOS: There are even experimental ways to use exFAT on very old DOS computers, though they are not common.
You can rename exFAT drives easily in Microsoft Windows Explorer. On Linux, you use special tools like `exfatlabel` and `tune.exfat`.
See also
In Spanish: ExFAT para niños
- Design of the FAT file system
- List of file systems
- Comparison of file systems
- Memory Stick XC
- Universal Disk Format
External links
- exFAT specification
- File System Functionality Comparison of exFAT, FAT32, NTFS, UDF
- exFAT overview in Windows Embedded CE
- Transaction-Safe FAT File System (TexFAT) overview in Windows Mobile 6.5
- Personal Storage : Opportunities and challenges for pocket-sized storage devices in the Windows world (PowerPoint presentation at WinHEC 2006)
- exFAT File System Licensing
- Reverse Engineering the Microsoft exFAT File System, SANS Institute.
, "Quick Filename Lookup Using Name Hash"; Microsoft Corp; contains exFAT specification revision 1.00. , "Contiguous File Allocation In An Extensible File System"; Microsoft Corp.
- exFAT ships on all SDXC Cards, SD Card Association
- The Extended FAT file system:Differentiating with FAT32 file system, Linux Conference, October 2011.
- Benefits of exFAT over FAT32
he:ExFAT