Thanks for the suggestions. There has been some work to make formatting more customizable (<a href="https:&#x2F;&#x2F;github.com&#x2F;cppformat&#x2F;cppformat&#x2F;issues&#x2F;235" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;cppformat&#x2F;cppformat&#x2F;issues&#x2F;235</a>). This will enable extensions like the ones you suggest while keeping the library itself lean. Generally useful extensions like thousand separators can be added to the core library of course. They are actually on my TODO list.