If I inspect ./fonts/ttf/OpenSans-Regular.ttf I see there is no U+202F NARROW NO-BREAK SPACE. Since it's a whitespace, some renderers fall back to U+2009 THIN SPACE but for great and reproducible typography this space is needed.
Examples of usage
Some examples in German for dates, units and phone-numbers:
If I inspect
./fonts/ttf/OpenSans-Regular.ttf
I see there is noU+202F NARROW NO-BREAK SPACE
. Since it's a whitespace, some renderers fall back toU+2009 THIN SPACE
but for great and reproducible typography this space is needed.Examples of usage
Some examples in German for dates, units and phone-numbers:
Source
Inspection
Source