Files with C4 extension store compressed graphics. This format consists of properly indexed image tiles. C4 files come in variants. Not all C4 files open in graphics programs. The US Department of Defense used this format. Now rarely used, C4 is obsolete.
What to do if a C4 file does not open? All common C4 issues can be fixed by users. The process is quick. It does not need IT experts. Follow the steps below to fix problems opening C4 files.
First, install XnView or a program that opens C4 files. If your antivirus blocks the file, take precautions. Recover or remove infected files. Scan the full system afterward.
Next, associate the program with C4 files. Right-click the file. Open with another application. Add the program location. Choose to always open C4 files with this program.
C4 files use raster image format. Programs like XnView might open some C4 files. But C4 file variants mean some files do not open. Update the software to handle the C4 format. Or scan for viruses blocking the file.