I was surprised when I saw the question Chinese text isn't working on Stack Overflow. I've seen questions and answers with Chinese characters all over Stack Exchange (Skeptics, Islam, Politics, Language Learning, History, not to mention virtually every question at Chinese, and Stack Overflow meta), so I didn't even realize there is anti-spam block on Chinese characters.

The above-mentioned question was closed as a duplicate of Not all UTF-8 characters supported and Unable to post Chinese characters due to validation filter, which explains why that user encountered a block at Stack Overflow (anti-spam), but it looks like the details of the answers are not up to date.

Question: Under what conditions are 漢字 blocked?

汉字 (simplified) / 漢字 (traditional) (hàn​zì​): Chinese character / CL: 個|个 / Japanese: kanji / Korean: hanja / Vietnamese: hán tự

I'm interesting in finding out:

  1. Which characters are blocked (e.g., Chinese, Japanese, Korean). I'm guessing it's some Unicode range.
  2. On which sites they are blocked.
  3. In which fields they are blocked (titles, question body, answers, tags, comments etc.)
  • 1
    Those specific characters or does 汉字 mean something specific?
    – Journeyman Geek Mod
    Jul 6 at 23:39
  • 3
    @JourneymanGeek 汉字 means "Chinese characters"
    – Smitop
    Jul 6 at 23:40
  • 1
    I switched to the traditional 漢字. In Chinese it means "Chinese characters", but it's also relevant for Japanese, Korean, and Vietnamese. Jul 6 at 23:52

1 Answer 1


Answering my own question... As we know, it's an anti-spam feature (but probably helps out preventing questions in the wrong language too). So some of the details here are unable to be revealed; I also don't know/understand them.

I now feel it's wrong to think of this feature as anything like a "ban on Chinese characters at certain sites", even at Stack Overflow. There are plenty of examples of questions on Stack Overflow containing Chinese characters:

Searching for common Chinese characters like or gives thousands of posts containing them.

All in all, Chinese text isn't working on Stack Overflow is best thought of as a sporadic false positive (at least, that's my impression). In the end, the question was posted and contains Chinese characters: Given an offset dictionary and a string, create the BIO tags.

This is why I (and others) have been able to widely use Chinese characters all over Stack Exchange without even noticing this feature exists.

  • 2
    Strong chance someone did a statistical analyses and there's an undisclosed heuristic to catch common spam sentences+keywords also depending on length... Just probing for common characters is unlikely to hit the filter, @alvas' example did contain paragraphs of prose and as a whole it somehow hit the filter.
    – bad_coder
    Jul 7 at 23:16
  • 1
    Indeed. It was closed as a duplicate of questions where single characters were enough to lead to it being blocked, which gave me the impression that there was a kind of "Chinese character block" on some sites. But this seems to not (or no longer) be the case. Jul 7 at 23:24

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