Review of Project Fluent powered by the Slant community.
A localization system for natural-sounding translations.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Supports variables, conditionals, localization, and build-in + custom functions
Pro Free and open-source standard
It's led by Mozilla and owned by the community.
Cons
Con As of January 2020, it doesn't have many libraries for programming languages
It's supported for JavaScript and Rust, but everywhere else is a bit shoddy.