What Is an ECM File?

An ECM file is a disc image that supports better compression to reduce the overall file size

What to Know

  • An ECM file is a disc image created in the Error Code Modeler format.
  • ECM is the name of the command-line tool that uses this format, but Gemc works, too.
  • You can convert from ECM to BIN, ISO, or CUE.

This article explains what an ECM file is and how to open or convert one on your computer.

What Is an ECM File?

A file with the ECM file extension is a disc image, sometimes called an Error Code Modeler file. They store content without error correction codes (ECC) or error detection codes (EDC).

Shaving off ECC and EDC can save on download time and bandwidth since the resulting file is smaller. The point is to then compress the file with a general compressor, like RAR, or another compression algorithm, to reduce the file size even more (they might then be named something like file.ecm.rar).

Like ISO, ECM files hold other information in an archive format, usually to store files like BIN, CDI, NRG, etc. These are often used to contain compressed versions of video game disc images.

Something called Cmpro examples might also use the ECM file extension, but there isn't much information on it.

How to Open an ECM File

ECM files can be opened with ECM, a command line program by Neill Corlett, the developer of the format (see their How ECM Works for additional information on the format). The How to Use the ECM Program section below provides information on how to use the tool.

ECM commands

ECM files also work with Gemc, ECM GUI, and Rbcafe ECM.

Since the file can be compressed to an archive like a RAR file to save on hard drive space, it might first have to be decompressed with a file zip/unzip utility—our favorite is 7-Zip.

If the data inside the file is in the ISO format, see How to Burn an ISO File to a DVD if you need some help getting it on a disc. You can also put an ISO file on a USB drive.

ECM files that aren't disk images might be usable with a simple text editor like Notepad in Windows, or something more advanced from our Best Free Text Editors list.

How to Use the ECM Program

Encoding (creating) and decoding (opening) an ECM file can be accomplished with Corlett's ECM program mentioned above. It's a command line utility, so the whole thing runs in a Command Prompt.

To open the ECM portion of the tool, extract the contents out of the cmdpack(version) ZIP file downloaded through the link above. The program you're after is called unecm.exe, but you have to access it through a Command Prompt.

cmdpack extracted files in Windows 10

The easiest way to do this is to drag the ECM file directly onto the unecm.exe program to extract the image file out of it. To make your own ECM file, drag the file you want encoded onto the ecm.exe file.

To do this manually instead of with drag and drop, open Command Prompt (you might need to open an elevated CMD) and then navigate to the folder that holds the ECM program. The easiest way to do this is to first rename the folder you extracted above to something simpler like cmdpack, and then enter this command:

cd cmdpack

This changes the working directly to the folder where the ECM program is stored. Yours will look different depending on where the cmdpack folder is located on your computer.

These are the commands you're allowed to use:

To encode:

ecm cdimagefile
ecm cdimagefile ecmfile
ecm e cdimagefile ecmfile

To create an ECM file, enter something like:

ecm "C:\Others\Games\MyGame.bin"

In that example, the file will be created in the same folder as the BIN file.

To decode:

unecm ecmfile
unecm ecmfile cdimagefile
ecm d ecmfile cdimagefile

The same rules apply for opening/decoding the ECM file:

unecm "C:\Others\Games\MyGame.bin.ecm"

How to Convert an ECM File

This tutorial at StramaXon provides an easy way to convert ECM to BIN. The download mentioned on that site is in the RAR format, so you'll need a program like PeaZip or 7-Zip to open it.

Once you have the ECM file in the BIN format, you can convert BIN to ISO with a program like MagicISO, WinISO, PowerISO, or AnyToISO. Some of these applications, like WinISO, can then convert ISO to CUE if you want your file to ultimately be in that format.

Still Can't Open It?

Some file formats share some or all of the same file extension letters, but it doesn't mean they're in the same format. This can be confusing when trying to open your file because it might not actually be an ECM file... double-check the file extension to be sure.

For example, you might be confusing it with an EMC file, which is an encrypted document used with Striata Reader.

MindMaple documents that use the EMM file extension are similar.

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