The latter. But you should realize Google is pretty conservative internally in the main repository because of the amount of code/tooling/etc. While we let people experiment in the main repository, they are controlled experiments. Even if we decided, tomorrow, to move the main repositories away from our current set of programming languages, that would be a fairly long term path, not a short one.

Outside of the main repository, or on google open source projects, or etc, people can generally do what they want, they just don't get the benefits of the above if they aren't using a language we already support very well.

So which languages are use internally in the main repository then?

What category are you looking for?

Supported or used or being experimented with or what?

Java, C++, Python, Golang, and Swift/ObfC for iOS apps

No JavaScript? Or is that because it's not used internally but in the public internet?

Google's "big" client apps (Inbox / Gmail / Calendar) are a mix of Java converted to JS (GWT) and native JS with the Closure library/compiler. I think, anyway.

Not sure if GWT is still that relevant nowadays. AngularJS was developed by Google many years ago. It was already pure JS.

Inbox by Gmail launched in 2014, long after Angular JS was first released, and uses GWT.

Close. Apps is using mostly using j2cl.

As addition to JavaScript, they have used their own language called Dart for some their services like AdWords or AdSense [1].

[1]: https://www.dartlang.org/community/who-uses-dart

JavaScript and Typescript should be in the list, as should Dart.

You should let Ericsson know the language that powers their telecom systems is an experiment.

Pretty clear that DannyBee was referring to their particular Elixir deployment environment, rather than to Elixir as a language, no?

It's FUD aimed at a particular language, though. If you know anyone inside Google you probably know how regularly people "experiment" without pushback; all of the internal Dart projects, for example.

Being the person in charge of the new language process, I'm just going to tell you your information is not correct.

Can you explain to me then how Elixir is more experimental than Go was when it was deployed in its early days?

Err, I thought I was quite clear that the experiment is people using the new-to-google language, not the language itself

I think it's pretty well known that the approved internal Google languages are Java, C++, Go, Python. Could someone correct me if I'm wrong?