86F File

What are 86F files and how to open them

Are you having problems opening a 86F 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 86F files.

What is a 86F file?

A .86F file is a 86Box Floppy Disk Image file.

86Box Floppy Disk Image files store exact recordings of floppy disk surfaces at the magnetic flux level, not just sector files. They capture the patterns of bits as a real floppy drive would read them (including so-called "weak bits," holes, or special magnetic behavior) in FM or MFM encoding. These images are used by the 86Box emulator to simulate floppy drives with high fidelity.

These files are produced and consumed by 86Box itself: the emulator allows you to load various floppy image formats and save ("export") them into .86f form to preserve fine-grained surface timing and encoding. You might use a .86f if you want accurate behavior in the floppy drive emulation (booting systems relying on weak bits, for example), rather than just the file-system contents.

Internal file structure begins with a 4-byte magic value "86BF" at offset 0. The header (from version 2.12) encodes version numbers and a 16-bit flags field controlling metadata like whether surface descriptions (weak bits or holes) are included, number of sides, write protection, RPM behavior, disk type (fixed or zoned RPM), zone type for certain formats, endianness of bit streams, and extra bitcell count. Following the header are entries for each track+side: a 16-bit track flags word, optional extra bitcell count, index hole position, then the actual FM/MFM (or related) encoded data for the track, and optionally per-bit surface description data.

How to open 86F files

Important: Different programs may use files with the 86F file extension for different purposes, so unless you are sure which format your 86F file is, you may need to try a few different programs.

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: August 16, 2026

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