CHI File

What are CHI files and how to open them

Are you having problems opening a CHI 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 CHI files.

What is a CHI file?

CHI files have multiple uses, and Chip Tracker Module is one of them. Read more about the other uses further down the page.

Chip Tracker Module

Chip Tracker Module files store tracked music designed for the AY sound chip in a module format created by the Chip Tracker tracker for the ZX Spectrum. They bundle melody patterns, sample data, and playback order into a single file so that the song can be played by a compatible player exactly as composed.

The files are produced by the Chip Tracker editor and compiler, which allow composing music in multiple channels (named A, B, C, D), defining samples, arranging patterns, setting tempo and loop points. After composition, the module is exported to this format so that a player program can read it and play back all the stored patterns and samples.

Internally the module is divided into four main parts aligned to sector boundaries: the header, the order list (positions where patterns are played), the pattern data themselves, and the raw sample data. The header (first sector) begins with the ASCII identification string CHIPv1.0. It also includes track title (32 bytes), tempo (1 byte, measured in units of 1/50 second), song length, loop position, parameters for up to 16 samples including loop start and length, reserved bytes, sample names (8 bytes each). The order list takes one sector, listing pattern numbers (0 - 30) in play sequence. Each pattern is 512 bytes, split into two 256-byte halves; each has 64 rows. Notes are encoded per channel with a byte for note and song-data in first half, then sample number, effect code and effect parameter in second half. Samples are stored as unsigned 8-bit PCM, aligned to sector boundaries. Unused samples use zero positions and lengths; non-looped samples have padding of value 128 and empty samples omitted. Maximum size for sample data allows up to 187 sectors for samples.

Byte signature beginning at offset 0 is "CHIPv1.0" (ASCII). The format uses this signature to distinguish it from others.

How to open CHI files

Important: Different programs may use files with the CHI file extension for different purposes, so unless you are sure which format your CHI 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 CHI openers which you will find listed below.

Last updated: August 31, 2026

All known file formats using extension .CHI

While Chip Tracker Module is a popular type of CHI-file, we know of 3 different uses of the .CHI file extension. Different software may use files with the same extension for different types of data.

ChiWriter document

These CHI files contain the GUI and the bitmap fonts with a fixed width used in ChiWriter, a text-editor used on MS-DOS, a Microsoft operating system. CHI files are mostly used for the speed and interactivity of editing rather than on the visual appearance. ChiWriter is used to add lines of text, half of the base line-height, above or below the current text.

Windows HELP Index

Windows Help Index files are navigation support files created by Microsoft's HTML Help system to enhance help documentation collections. They are used when several compiled help modules are merged or when a master help file is combined with component help files. They store index data so users can search topics across multiple CHM help files from a central location.

These files are written by the HTML Help compiler or by the master CHM file's merge process. When component help files are installed together, the compiler or Windows Help will generate a merged index file so that the main help viewer can display a unified index. While the main content resides in CHM files, the index records in this file speed up finding topics spread across those CHM files.

Technical details: files use a binary format compatible with the ITSF (Information Technology Storage Format) container used by CHM files. Their structure includes merged index trees, not simple site maps. They begin with distinctive byte signatures; for instance, one signature starts with bytes 49 54 53 46 03 00 00 00 60 00 00 00 01 00 00 00 at offset zero.

Various apps that use files with this extension

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

Help us help others

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