Hi all, Here I want to encode OrderedDictionary to JSON file, I use the JSONEncoder below: let encoder = JSONEncoder() encoder.outputFormatting = [.prettyPrinted, .withoutEscapingSlashes] and I declare variables qwe, asd and zxc: var qwe = OrderedDictionary<String, Int>() qwe["bbb"] = 12 qwe["ccc"] = 13 qwe["ddd"] = 14 qwe["bbc"] = 15 var asd = Dictionary<String, Int>() asd["bbb"] = 1 asd["ccc"] = 3 asd["ddd"] = 4 asd["bbc"] = 5 var zxc: KeyValuePairs<String, String> { return [ "zz": "zz", "aa": "aa", "bb": "bb", "cc": "cc", "bc": "bc", ] } After I do try encoder.encode(qwe).write(to: path ,options: .atomic) encoder.encode(asd).write(to: path ,options: .atomic) encoder.encode(zxc).write(to: path ,options: .atomic) the output JSON file format of OrderedDictionary isn't what I expected. The output JSON of OrderDictionary is like this: [ "bbb", 12, "ccc", 13, "ddd", 14, "bbc", 15 ] On the other hand, the output JSON of Dictionary and KeyValuePairs are normal, just with different order: Dictonary: { "ccc" : 3, "bbb" : 1, "bbc" : 5, "ddd" : 4 } KeyValuePairs: { "cc" : "cc", "aa" : "aa", "zz" : "zz", "bb" : "bb", "bc" : "bc" } I also Log these objects after I declare them, the Log show their structure are similar: qwe -> ["bbb": 12, "ccc": 13, "ddd": 14, "bbc": 15] asd -> ["ccc": 3, "bbb": 1, "bbc": 5, "ddd": 4] zxc -> ["zz": "zz", "aa": A"aa", "bb": "bb", "cc": "cc", "bc": "bc"] I thought the OrderedDictionary is similar to Dictionary, but does anyone know why the output of OrderedDictionary is not like this: {"bbb": 12, "ccc": 13, "ddd": 14, "bbc": 15} Or is there any other way I can customize the order of keys in my encoded JSON file? Thank you so much!