Can I stretch a square or narrow desktop to fill my display?

Yes, as a streaming workaround: create a virtual screen with the shape you want, stream it to the physical display, and enable Free Aspect Ratio. This lets the streamed image fill a differently shaped target without preserving the source’s proportions. It requires Pro and Screen Recording permission.

1. Create and connect a virtual screen with your desired aspect ratio—for example, 1:1 for a square desktop.
2. In that virtual screen’s streaming menu, select the physical display as the target.
3. Turn off 1:1 Pixel Mapping, then enable Free Aspect Ratio in the stream’s transformation options. The free-aspect option is unavailable while direct pixel mapping is enabled.
4. Put the app or game on the virtual desktop so its image is the one being stretched.

Stretching changes the image’s geometry: circles can become ovals, and text and interface elements become wider or taller. It does not change the panel’s physical shape or guarantee that a game will expose a particular internal rendering resolution.

Streaming also adds a capture-and-presentation step. Test pointer interaction, latency and performance with your application. A smaller source desktop is not a guarantee of faster gameplay. See Streaming and interacting with the source desktop.