Inverts the video so it is the mirror reflection
F11or the Electron Capture app (right-click → Resize window -> Fullscreen) to hide the browser menu instead.
If you are looking for a form of rotation and flipping that rotates the actual video, rather than relying on CSS to achieve it, you can check out the sender-side
https://vdo.ninja/beta/?effects=-1, which will flip the video
https://vdo.ninja/beta/?effects=-2, which will flip and mirror the video
https://vdo.ninja/beta/?effects=2, which will mirror the video Effects however may increase CPU/GPU usage, and could cause frame rate instability, especially if the browser tab is not in active focus.
There's a dedicated tool for mirror, flipping, and rotating websites as part of VDO.Ninja as well:
In case the built-in options to mirror or flip don't work, the teleprompter app might be a good alternative.