Files with the .CHW extension contain many HTML Help (CHM) files compiled in a way that allows for free navigation between them. They contain an index - a table of contents of help files with references to each of them. Each time individual CHM files are changed, the CHW file must be rebuilt again to keep the table of contents up to date.

CHW files are not compressed by default, so they can be very large. Use specialized software compress them, for example KeyCHW or FAR Helpware Group – this will significantly reduce the size of the CHW file. The FAR application also allows you to view the content of a selected file after selecting the Authoring - Help File Explorer option from the menu.