# Chapter 10. The File Format Of .cw Files

In this chapter, we briefly describe the format of `.cw` files, the file format Qt Designer uses for custom widgets.

Each `.cw` file starts with `<!DOCTYPE CW><CW>` and ends with `</CW>`. Between these lines, there are custom-widget descriptions, as explained in the section called The Description Of The Used Custom Widgets in Chapter 9. The only difference is that pixmaps are inlined directly and not collected at the end of the file.

The Description Of The Tab-Chain |  |