DI File

What are DI files and how to open them

Are you having problems opening a DI file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your DI files.

What is a DI file?

DI files have multiple uses, and Smaky Disk Image is one of them. Read more about the other uses further down the page.

Smaky Disk Image

Smaky Disk Image files are disk images made specifically for the Smaky Infini emulator developed by EPSITEC SA in Switzerland. They replicate a Smaky computer's disk so that the emulator can treat the virtual disk just like a real Smaky floppy or disk volume. These images let software that ran on the original Smaky hardware be stored, shared, backed up, and used on modern PCs through Smaky Infini.

The files are created by Smaky Infini or tools intended for it. Once produced, a disk image may be mounted or loaded into the emulator to provide file storage, install or run software, or preserve user documents. The image behaves like a complete Smaky disk, including its directory structure and contents, under the emulator's virtual drive system.

Internally, a Smaky Disk Image file begins with a fixed signature: at offset zero it contains the ASCII text "EPSITECSA" followed by a space, "SA", and a zero byte ("EPSITECSA SA\0"). This distinguishes it from other disk image formats.

How to open DI files

Important: Different programs may use files with the DI file extension for different purposes, so unless you are sure which format your DI file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested five different DI openers which you will find listed below.

Last updated: October 27, 2026

All known file formats using extension .DI

While Smaky Disk Image is a popular type of DI-file, we know of 2 different uses of the .DI file extension. Different software may use files with the same extension for different types of data.

XL/ST Link / XLDJ Disk Image

XL/ST Link / XLDJ Disk Image files store a complete copy of an Atari floppy disk as used by the XL/ST-link or XLDJ disk drive emulators for the Atari 8-bit line (not the ST line) including the 800XL model. They capture all recorded disk sectors, along with metadata to allow faithful emulation of the disk's structure and contents.

These images are produced by the disk drive emulator software called XL-DJ, written by Kolja Koischwitz & Christian Krueger, which works with Atari's 1050/XF551 drives via emulation. The emulator writes disk sector images, headers, and checksums. The emulator (the creating program) uses the file to recreate a virtual floppy disk when mounted, so that Atari software expecting physical media can read from it exactly. At runtime, sectors marked as unused or with zero checksum are omitted and re-inserted as blank on read. The format is not used by Smaky or other disk systems despite sharing the same file extension in some cases.

The file begins with a header: two ASCII characters 'D' and 'I' followed by bytes 0x20, 0x02; after a creator program name string it records the number of tracks (byte), number of sectors per track (big-endian word), sector size (big-endian word), and flags. Following the header is a sector table listing one checksum byte per sector (tracks × sectors per track). The body stores only sectors whose checksum in the table is non-zero, concatenated in track/sector order. Checksum is computed by summing all bytes of the sector with carry (e.g. 0xFF + 0x01 wraps to 0x01).

Various apps that use files with this extension

These apps are known to open certain types of DI files. Remember, different programs may use DI files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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File.org helps thousands of users every day, and we would love to hear from you if you have additional information about DI file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.