[drybjed]

YAML, TOML and JSON can be ingested to represent the same data structures internally, it's just a few lines of code to decide which load() function should we use for a particular file. Why not support all three formats in your applications for configuration and just let users decide, which one they want to use? Put a 'config.json' in '/etc/app/conf.d/' and you get the same data, as with 'config.yml' or 'config.toml'. Then users can use whichever format they prefer for the input data.

[MrDarcy]

I tried this, it significantly complicated documentation and support after release. Lots more logic handling conflicting cases in two otherwise identical files, etc.

[cyanydeez]

clarification: YAML and TOML can represent JSON, but the opposite isn't true.