At Stack Overflow for Japanese (SOja), we can use full-width alphanumeric characters for tags. In Japanese, these characters are used almost the same as their half-width version.


half-width: a
full-width: a

half-width: 1
full-width: 1

At SOja, we prefer to use half-width characters for tags, and the system also tends to support to use half-width tags. In fact, at SOja, a tag written by full-width alphanumeric characters are usually identified with its half-width version. For example, if we move a mouse cursor on a tag [c], it shows a tag description of a tag [c].

A screenshot of a tag description of the full-width c

They, however, are not tag-synonyms. We can still tag a question by a full-width one. Searching by a tag is also treating them as different tags.


Also, it seems that low-rep users can use a full-width tag if its half-width version exists. For this reason, it often happens that full-width tags are used wrongly.

Currently, SOja users correct these tags by hand, which is time-consuming. Related issues were post to SOja Meta in the past (1, 2), but a SOja manager at that time said "This is difficult to fix. The root cause of this problem is the difference of character handling between SQL and C#".

But it is troublesome to check all tags and detect full-width characters manually. Is it possible to avoid creation of tags with full-width alphanumeric characters? For example, can we restrict these characters (say, U+FF01...U+FF5E) for tags? Or, can we treat them as half-width characters like tag synonyms?

  • 2
    How extensive is this? Can these full width characters only be used on SOja, on international sites, or can they be used for tags any Stack Exchange site? Feb 12, 2020 at 2:08
  • 1
    @1201ProgramAlarm Nice comment. I also want to know that. I cannot fully confirm that due to my low reputation at other sites. At least I confirmed that I cannot tag a question with full-witdh [c] at SOen on the question creation page /questions/ask, but can tag at SOes.
    – nekketsuuu
    Feb 12, 2020 at 3:22
  • 1
    I made a quick edit to test, and while it allowed me to create a tag named testingg, it didn't allow that for tesuto. So maybe this is only enabled on SOja (+ possibly other international sites).
    – muru
    Feb 12, 2020 at 3:27
  • 3
    I admit to not being an expert in typesetting but I wouldn't even now how to make full vs half width characters... and I don't even know what the characters I type with are... so that kinda argues that maybe it's not even a thing people think about in English?
    – Catija
    Feb 12, 2020 at 3:47
  • 3
    @Catija English = halfwidth, I believe. To type in fullwidth usually you'd use an IME to convert keyboard input into a different character set. example Feb 12, 2020 at 3:56
  • 4
    Also at Chinese.SE, e.g. . Feb 12, 2020 at 4:50
  • 3
    O r j u s t t y p e a s p a c e i n b e t w e e n e a c h c h a r a c t e r t o s e e h o w r e d i c u l o u s t h i s l o o k s.
    – Luuklag
    Feb 12, 2020 at 8:23
  • And then the comment editor removed all my doubled up spaces...
    – Luuklag
    Feb 12, 2020 at 8:23
  • 6
    @Luuklag No, full-width alphanumeric characters are commonly used in order to make typographic harmony with Japanese Hiragana/Katakana/Kanji, which are full-width by default. So they are not margined half-width characters, but characters designed for the special purpose. Here, we SOja users want to use half-width characters for a tag name because it often contains English words.
    – nekketsuuu
    Feb 12, 2020 at 8:34
  • We've reviewed this request and have moved it to our backlog. I've updated the status to status-deferred. (I meant to leave this comment when I edited tags earlier, but forgot.)
    – V2Blast
    Feb 23, 2023 at 18:17


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