How to open CTO files

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

What is a CTO file?

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

While we do not yet describe the CTO 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 CTO 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 CTO

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

ChessBaseChessBaseUser submitted
ChessBase LightChessBase LightUser submitted
ChessBase ReaderChessBase ReaderUser 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 CTO-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 CTO-files. If you know one, please use the Suggest link below and tell us about it!