Firefox opens new window not tab
Firefox opens a new window rather then tab from any other process calling firefox. Example screen grab utility needs to load a new url. FF opens a new instance of firefox. It use to open a new tab.
Opaite Mbohovái (1)
This issue can be caused by an extension that isn't working properly.
Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).
- Do NOT click the Reset button on the Safe mode start window or otherwise make changes.