A CPIO archive is uncompressed, which is why GZIP is applied to the file—so that it can be compressed to save on disk space. In these archives might be software programs, documents, movies, and other types of files. TGZ is a similar format that compresses a TAR file (which is also an uncompressed file container) with GZIP compression.
How to Open a CPGZ File
CPGZ files are typically seen on macOS and Linux operating systems. The ditto command-line tool is one way you can open one in those systems. However, if you’re running Windows, we suggest trying PeaZip, 7-Zip, or some other file compression/decompression program that supports GZ compression.
How to Open a .ZIP.CPGZ File
One strange scenario where you may unexpectedly find a CPGZ file is when you’re trying to open a ZIP file in macOS. The OS may create a new file with the .ZIP.CPGZ extension instead of actually giving you the contents of the ZIP archive. When you open it, you find the ZIP file again. Decompressing it gives you back a file with the .ZIP.CPGZ extension…and this loop continues on, however, many times you try opening it. One reason this may happen is because macOS doesn’t understand what type of ZIP compression is being used on the file, so it thinks that you want to compress the file instead of decompress it. Since CPGZ is the default format used for compression, the file is just being compressed and decompressed over and over again. One thing that might fix this is to just download the ZIP file again. It may not be opening correctly if the download was corrupted. We recommend trying a different browser the second time, like Firefox, Chrome, Opera, or Safari. Some people have had success opening the ZIP file with The Unarchiver. Another option is to run this unzip command in a terminal:
How to Convert a CPGZ File
The best way to convert the files inside a CPGZ file is to first extract them out of it using one of the file decompressors from above. Once you have the contents isolated, you can use a free file converter to convert them to a different format. We say this because CPGZ is just a container format, meaning it contains other files inside it—it’s not meant to be directly converted to a format like XLS, PPT, MP3, etc. For example, if you’re trying to “convert” CPGZ to PDF, you need to instead use a file unzip tool like one we already mentioned. This will let you take out the PDF, which you can then treat like you would any other one and convert it using a document converter. The same is true if you want to convert CPGZ files to SRT, IMG (Macintosh Disk Image), IPSW, or any other file type. What you really need to do, instead of converting the CPGZ archive to those formats, is decompress the archive so that you can open those files normally. The same file decompression utilities we already mentioned can be used to open these CPGZ files, too. It’s not necessary to convert one to other archive formats like ZIP, 7Z, or RAR since they’re all used for practically the same purpose: to store files. However, if you want to, you can do this manually by just extracting the files out of the archive and then compressing them to ZIP (or another archive format) with a program like 7-Zip.
