[vitaut]

{fmt} doesn't encourage "custom formatter specification to live in a template". On the contrary, if you look at the docs in https://fmt.dev/latest/api.html#formatting-user-defined-type..., none of the examples is parameterized. One even demonstrates how to define your formatting code in a source file. And if your formatters are so big that they meaningfully impact build speed you are doing something wrong. fmt/core.h is heavily optimized for build speed so you can just use it as a type-safe replacement for *printf. That said, implementations of std::format (especially Microsoft's) may not be as optimized for build speed yet. This will likely improve now that the ABI can be stabilized.