1. run the zul
Only found on Windows Chromium-based browsers. The image below was captured on macOS Chrome 85.
both have the same height by default.
Font awesome is a built-in icon set, users would expect it works by default without any issue. Therefore, a button with an icon should look consistent in size.
Depends on the user agent. Desktop browsers (including Firefox) use a default value of roughly 1.2, depending on the element's font-family.
Since the used font-family is different between macOS (Helvetica Neue) and Windows (Arial), it could be a root cause.