Liquid filter suited for Jekyll that generates pretty JSON output.

pretty_json.rb

module Jekyll
  module PrettyJsonFilter

    def pretty_json(input)
      begin
        JSON.pretty_generate(input)
      rescue JSON::GeneratorError => e
        "Error: #{e}."
      end
    end

  end
end

Liquid::Template.register_filter(Jekyll::PrettyJsonFilter)

# USAGE:
# {{ site.data.user | pretty_json }}