Vertical lines down my laptop screen, is it the panel or GPU?

another one: restart and go into the BIOS. that screen doesn't use the graphics driver at all, so if the lines are there too it's hardware, not something a driver reinstall will fix.

Plug it into an external monitor or TV. If the lines show there too, it's the GPU. If the external screen is clean, it's the laptop panel or the cable running up through the hinge. Another quick one: take a screenshot and look at it on your phone. Lines in the screenshot mean graphics, not the screen. If they change when you move the lid, that points to the hinge cable, which is a much cheaper fix than a new panel.