SEGGER’s open BigFAT specification breaks FAT’s 4GB per file barrier

26 AUGUST 2022

SEGGER’s BigFAT specification, which enables any third party to store files larger than 4 GB on standard FAT media, is now publicly available. This specification is not encumbered by any patents and can be used freely, along with the supporting tools.

Supported by all operating systems, FAT is the industry standard for formatting removable storage such as SD cards and USB memory sticks.

Technical simplicity and universal support make it attractive even for applications running on resource-constrained devices such as mid-size microcontrollers.

It is also a great choice for transferring files between systems.

FAT’s main shortcoming is limited file size, which becomes apparent when storing or transferring video files or using databases.

SEGGER addresses this shortcoming with BigFAT, extending the FAT file system with support for files well beyond 1TB. BigFAT breaks large files into small pieces, each piece comfortably fitting on a FAT volume as an individual file, and presents these files as a single massive file to the user, while maintaining full compatibility with standard FAT.

SEGGER provides a free tool called BigFAT Converter, which runs on Linux, macOS, and Windows. It allows users to create, read, or copy BigFAT files to and from the host file system.

“FAT plays an important role in the Embedded Space,” says Rolf Segger, founder of SEGGER. “Whether used for removable storage media, such as SD cards and USB sticks, or as an internal file system, many embedded systems use FAT. exFAT, presented as successor to FAT for SD-cards, is unfortunately not compatible with FAT and is also patent encumbered.”

“Any company using or implementing exFAT requires a license from Microsoft, which can be difficult or costly to obtain, especially for small businesses and the Open Source Community,” says Ivo Geilenbruegge, Managing Director of SEGGER. “That’s why we at SEGGER decided to introduce BigFAT as open, non-patent encumbered specification. By allowing all interested parties to use BigFAT without charge or hassles, we aim to establish it as a new standard. Anyone is welcome to implement it based on the specification.”

SEGGER emFile PRO comes with an implementation of BigFAT.

For more information on BigFAT, please visit:
Learn more about emFile at:


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