I’m making a website, and using ISO standard two letter language codes for tagging user-submitted content. I’m not intending on adding every single language, but would like an other category. It’s not a huge problem, but it got me wondering, is there a standard code for other? If there is nothing official, is there a common convention?

2 Answers 2


Two-letter codes are defined in ISO 639-1 and the current list does not contain a code for "other". (As Wikipedia's list of ISO 639-1 codes shows, not all possible two-letter codes have been used so far, i.e. only 184 out 676 possible codes, so it is theoretically possible that such a code gets added later.)

Since the possible number of codes allowed by two-letter codes is much too low for the world's languages, ISO has defined three-letter codes in ISO 639-3. However, I am not aware of an ISO 639-3 code for "other" language. The standard has a few special codes for situations when you can't use a language code:

  • mis: for documents using uncoded languages, i.e. languages don't have a ISO code (yet);
  • mul: for documents using multiple languages (however, in markup languages, you can use the lang attribute on specific elements that contain content in a single language);
  • und: for documents where the language has not been identified;
  • zxx: for documents without any linguistic content.

The closest match with what you need is und.


In Addition to @Tsundoku's answer, there is a kind of private use area in ISO 639-3: In addition, 520 codes in the range qaaqtz are 'reserved for local use'. So you can assign in your application the code qot for "other" when you want to do this. Note that the same code can have completely different assignments on other places.

Addition in reply to the comments: There is no such option with ISO 693-1 two letter codes, all codes in there are assigned to languages.

  • OP specifies that they are using two-letter language codes, i.e. ISO 639-1, not ISO 639-3. From a quick look it doesn't seem that these codes have ISO 639-1 equivalents, or that there is any private use area in ISO 639-1 (although there are many unassigned code points), but this answer would be substantially improved by discussing ISO 639-1 explicitly, even if only to explain why it does not offer a good solution, and ISO 639-3 should be used instead
    – Tristan
    Commented Dec 1, 2020 at 13:29
  • the OP says "using ISO standard two letter language codes". The ISO standard two letter codes are ISO 639-1
    – Tristan
    Commented Dec 1, 2020 at 15:26
  • Ok, I see it now Commented Dec 1, 2020 at 15:31
  • no worries. The answer already addressed the underlying concern in the question, I just wanted to make sure the two letter case was explicitly addressed for anyone coming across it later
    – Tristan
    Commented Dec 1, 2020 at 15:41

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