MDN tells about this function:
The fit-content() CSS function clamps a given size to an available size according to the formula min(maximum size, max(minimum size, argument)).
and later about the state:
CSS Intrinsic & Extrinsic Sizing Module Level 3 The definition of 'fit-content()'. Working Draft
CSS Grid Layout The definition of 'fit-content()' in that specification.
Candidate Recommendation
But Firefox and Chrome just say "no". "Can I use …" does not even know this function.
My explanation is, that until now only the "CSS Grid Layout" context is supported, and "CSS Intrinsic & Extrinsic Sizing" is not.
But - is this the case? And when will it be available?