# libtmux::Window::expand

- **Module:** libtmux::Window
- **Package:** libtmux-cxx
- **Language:** C++
- **Kind:** method
- **Source:** https://github.com/libtmux/libtmux-cxx/blob/393d4b0ad666f18a6581f1eb281741a75a7503f0/include/libtmux/entities.hpp#L638
- **Page:** https://libtmux.org/en/cxx/latest/reference/libtmux-window-expand/

```
libtmux::Window::expand(format: std::string_view) -> expected< std::string, CommandFailure >
```

Ask tmux to expand a format against this window: the same reach the session form gives, guarded the same way.

A window that has gone reports `missing` rather than answering with a blank.