In this article, we explain what the meaning of FAT is relating to hard drives.
What is FAT? Which version should hard drives be formatted in? Pros & cons revealed.
When it comes to hard drives, “FAT” refers to File Allocation Table, a file system developed by Microsoft. It’s used to organize and manage files on storage devices like hard drives, USB drives, and memory cards. Over time, different versions of FAT have been developed, each with improvements and limitations. Below, I’ll explain the main variants: FAT12, FAT16, and FAT32, along with some context on how they differ and where they’re used.
1. FAT12
- Overview: The original File Allocation Table system, introduced in 1977 for floppy disks.
- Bit Depth: Uses 12-bit entries to address clusters (storage units on the drive).
- Max Partition Size: 32 MB.
- Max File Size: 32 MB.
- Cluster Size: Typically 512 bytes to 8 KB, depending on the disk.
- Use Cases: Primarily used on early floppy disks and very small storage devices.
- Limitations: Its small addressing space (12 bits = 4,096 clusters max) makes it impractical for modern hard drives. It’s inefficient for anything beyond tiny storage.
2. FAT16
- Overview: An upgrade from FAT12, introduced in 1984 with MS-DOS 3.0.
- Bit Depth: Uses 16-bit entries, allowing up to 65,536 clusters.
- Max Partition Size: 2 GB (with 32 KB clusters) or 4 GB (with non-standard 64 KB clusters, though not universally supported).
- Max File Size: 2 GB.
- Cluster Size: Ranges from 512 bytes to 64 KB, depending on partition size.
- Use Cases: Common in early hard drives, older USB drives, and some embedded systems.
- Limitations: The 2 GB partition limit became a bottleneck as storage needs grew in the 1990s. Larger cluster sizes also waste space (a problem called “slack”) on small files.
3. FAT32
- Overview: Introduced in 1996 with Windows 95 OSR2, it’s the most widely used FAT variant.
- Bit Depth: Uses 32-bit entries (though only 28 bits are actually used for addressing, capping at ~268 million clusters).
- Max Partition Size: 2 terabytes (practically) or 16 terabytes (theoretically, with 64 KB clusters).
- Max File Size: 4 GB (minus 1 byte).
- Cluster Size: 4 KB to 32 KB, depending on partition size.
- Use Cases: Still common on USB drives, SD cards, and devices needing broad compatibility (e.g., cameras, gaming consoles).
- Advantages: Supports much larger drives than FAT16 and is compatible across many operating systems (Windows, macOS, Linux).
- Limitations: The 4 GB file size limit is a big drawback in the era of HD video and large datasets. It also lacks modern features like file permissions or journaling (which helps recover from crashes).
Beyond FAT: exFAT and Others
While not a “FAT” in name, exFAT (Extended File Allocation Table) is a related evolution worth mentioning:
- Overview: Introduced by Microsoft in 2006 for flash drives and larger storage.
- Max Partition Size: 128 petabytes (effectively limitless for now).
- Max File Size: 128 petabytes.
- Cluster Size: Flexible, typically 4 KB to 32 MB.
- Use Cases: Ideal for external drives, SDXC cards, and situations needing files >4 GB.
- Advantages: Overcomes FAT32’s file size limit while retaining broad compatibility.
- Downsides: Not as universally supported as FAT32 (some older devices don’t recognize it), and it’s proprietary (licensing can be an issue).
Key Differences in a Nutshell
| Feature | FAT12 | FAT16 | FAT32 | exFAT |
|---|---|---|---|---|
| Bit Depth | 12-bit | 16-bit | 32-bit (28 used) | 64-bit |
| Max Partition | 32 MB | 2-4 GB | 2 TB (practical) | 128 PB |
| Max File Size | 32 MB | 2 GB | 4 GB | 128 PB |
| Compatibility | Very old | Old devices | Broad | Modern devices |
| Modern Use | Rare | Rare | USBs, SD cards | External drives |
How It Works (Simplified)
The “FAT” in these systems is like a map that tracks where files are stored on the drive. Each cluster (a small chunk of storage) gets an entry in the table. When you save a file, the system writes it to clusters and updates the FAT to remember which ones are used. The bit depth (12, 16, 32) determines how many clusters it can track, which in turn limits partition and file sizes.
Why It Matters
- FAT32 is still everywhere because it’s simple and works across platforms, but it struggles with modern file sizes.
- exFAT is the go-to for big files on portable drives.
- Older FATs (12/16) are mostly relics, though you might encounter them in retro computing or niche hardware.
If you’re formatting a drive today, FAT32 is fine for small stuff with wide compatibility, but exFAT is better for anything involving large files.
