BIN/CUE to CHD — Compressed Conversion for Emulators

About 3 min read · 2026-08-04

Run CD-based games on an emulator for a while and your files get messy fast. A single game arrives as one .cue and several .bin files, and a multi-disc game multiplies that.

CHD tackles the problem head-on. It puts the whole thing — track layout included — into one file, and compresses it too.

What CHD is

CHD is short for Compressed Hunks of Data, a container created by the MAME project. These days it is supported not only by MAME but by many RetroArch cores, DuckStation, PCSX-ReARMed and others.

Compared with BIN/CUE:

	BIN/CUE	CHD
File count	1 `.cue` + 1 to dozens of `.bin`	1
Compression	None	Yes
Track information	Kept separately in the `.cue`	Contained in the file
Audio tracks	Separate `.bin` files or regions	Preserved as-is

The key point is that it is lossless. Decompress it and you get exactly the original data back, so the game behaves no differently.

Converting

Open the BIN/ISO → CHD tool.
Drop the .cue and .bin in together.
Check the compression level (6 by default).
Press convert and you get one .chd per disc.

Including the .cue matters. How many tracks there are and which ones are audio is recorded only in the .cue, so uploading the .bin alone converts without that information. Games whose music is CD audio can end up silent.

Several discs at once

For a three-disc game, drop all three sets in. The discs are picked up in order and you get one CHD per disc. They are not merged into a single file the way EBOOTs are, because emulators handle disc swapping at the file level.

Choosing a compression level

Levels run from 0 to 9, with 6 as the default.

Level	Result
0	No compression. Only bundles the tracks, so the size does not drop
6	Default. A balance of size and time
9	Smallest output, at a steep cost in conversion time

Level 0 is for when you are thinking "I don't care about the size, I just want the files tidied up." If you actually want space back, 4 or above is worth using, and for most people the default of 6 is plenty.

Compression ratios vary a great deal by game. A game that is mostly data can shrink by nearly half, while one that is mostly pre-compressed video will barely budge.

Using CHD in an emulator

As a rule, a CHD goes wherever you used to put the .cue.

RetroArch — pick the .chd directly under Load Content. Beetle PSX, SwanStation and most other CD-based cores support it
DuckStation — CHD files show up in the game list as they are
MAME — CHD is native territory here, so there is nothing to worry about

For software that does not support it, you will have to unpack back to BIN/CUE.

The order when combining with a translation patch

Apply the patch first, then convert to CHD.

A patch is written against byte positions in the original .bin. Once it has been compressed into a CHD, that structure is entirely different and the patch can no longer be applied.

Original BIN/CUE  →  apply patch  →  convert to CHD  →  emulator

To patch a file you have already turned into a CHD, you have to unpack it back to BIN/CUE, patch it, and convert again. Keeping to the order from the start is far less work.

Detailed patching instructions are in How to Apply a Translation Patch.

Common problems

No background music in the converted CHD You most likely converted the .bin without the .cue. Try again with the .cue included.

The size barely went down Either the compression level was 0, or most of the game data is already-compressed video and audio. If raising the level makes little difference, it is the latter.

The emulator will not read the CHD The core may be out of date. On RetroArch, try updating it. If that does not help, that core simply does not support CHD and you will need BIN/CUE.

I am not sure the converted file is correct Drop the original .cue into the file inspector to see how the track layout is being read. Confirming that the tracks are recognised correctly before converting heads off problems early.

Summary

CHD is a lossless compressed container that carries track information too
Always include the .cue — the audio track information is in there
The default level is 6; level 0 does not compress at all
Keep to the order: patch, then convert to CHD

The broader question of which format to choose is covered in Disc Image Formats.