How to open 666 files

Did your computer fail to open a 666 file? We explain what 666 files are and recommend software that we know can open or convert your 666 files.

What is a 666 file?

The 666 file extension indicates to your device which app can open the file. However, different programs may use the 666 file type for different types of data.

While we do not yet describe the 666 file format and its common uses, we do know which programs are known to open these files, as we receive dozens of suggestions from users like yourself every day about specific file types and which programs they use to open them.

We are continually working on adding more file type descriptions to the site, so if you have information about 666 files that you think will help others, please use the Update Info link below to submit it to us - we'd love to hear from you!

Generic 666

These apps are known to open certain types of 666 files. Since many different programs may use 666 files for different purposes, you may need to try a few of the apps to open your specific 666 file.

UltraZipUltraZipUser submitted
Pro/ENGINEERPro/ENGINEERUser submitted
Creo Elements/ProCreo Elements/ProUser submitted
CreoCreoUser submitted
Pro ENGINEERPro ENGINEERUser submitted
Startup TOOLSStartup TOOLSUser submitted
ProeWF3ProeWF3User submitted
UltraZip UIUltraZip UIUser submitted

Try a universal file viewer

Try a universal file viewer like Free File Viewer. It can open over 200 different types of files - and most likely yours too. Download Free File Viewer here.

We have not verified any programs that we know for certain can work with 666-files on Mac. If you know one, please use the Suggest link below and tell us about it!
We have not verified any online services that we know for certain can work with 666-files. If you know one, please use the Suggest link below and tell us about it!