What is the level of usage needed to be in this list?

[Thorium]

Does this mean "as a main language", i.e. when you join the company, you expect to do that on daily basis, or does this list contain also companies that use F# in some projects?

And how about enterprises that use them in tooling like Fake build scripts?
If Fake would be enough, I'd suppose all the ones in Paket testimonials would do.

[ReedCopsey]

I definitely wouldnt include paket users... That's a tool. Fake, at least, requires writing f#, so that's potentially interesting.

[Krzysztof-Cieslak]

Paket doesn't have anything to do with F# ;-)

[Thorium]

Maybe there could be a new column about usage? With options, i.e. frontend / backend / build and tooling / some microservices / ...

[jayhill]

My metric would be whether at least one job exists at the company where someone works in F# on a day-to-day basis or at least needs to maintain a production codebase with a nontrivial F# component, though they may not be touching that codebase on a daily basis.

It doesn't have to be exclusively F#, but to a degree that such a position — if/when it were open — would potentially be of interest to someone specifically seeking to work with F#.

[stianlagstad]

How about just asking the (subjective) question: How likely is it that a new hire gets to work with F#? With three possible answers: Low probability, medium probability, and high probability.

[pchalamet]

As a codebase is rarely fully F#, developpers shall expect anyway to use daily this lang from companies on this list.

A little bit off-topic but to have a better grasp why companies are on the list: it would be nice to see where it's used (backend, frontend, tests, datascience...) and maturity level (poc, production, maintenance only, ...). Probably latter would scare a little bit people, but for job seekers, this could be really valuable.