The issue you are experiencing is not a flaw specific to Internet Explorer 11 alone (Firefox also exhibits the same behavior as IE11). It is actually a result of using Segoe UI Light as a regular weight and a limitation of Segoe UI on Windows 7, where there is no proper italic face available for the Light weight. When you apply font-weight: bold
to text set in Segoe UI Light, it appears as faux bold because there is no true Bold face for this font. Similarly, applying font-style: italic
results in faux italics since an italic face does not exist for Segoe UI Light.
Google Chrome seems to address the issue with font-weight: bold
by automatically selecting the Bold weight when detecting the Segoe UI family, instead of resorting to faux bold. This behavior, inherited from WebKit, suggests that Safari would likely exhibit similar behavior with comparable font families on macOS. The display of proper italics is successful because Windows 7 includes a Segoe UI Bold Italic face. Surprisingly, on Windows 10 (and even Windows 8/8.1), Google Chrome renders bold text using Segoe UI Semilight, despite having font-weight: bold
specified in its UA stylesheet for b
elements. This deviates from the expected behavior of choosing the Bold face over the Semilight face, but the reason for this inconsistency remains unclear.
To resolve these inconsistencies, ensure your font family is set to Segoe UI, set title font weights to 300
for Light, then adjust bold parts to 600
for Semibold or bold
or 700
for Bold as per preference. Following these steps should yield the desired bold and italic styles. Remember that authentic italics are only fully supported for Segoe UI Regular and Bold on Windows 7, whereas nearly all weight variants of Segoe UI on Windows 8/8.1 and Windows 10—ranging from Light to Black—support italics functionality.