I tried to create a tag on SO that contained a plus character ("+"), but instead two separate tags were passed in. How can I create a tag that contains "+"?

  • 2
    My previous reply was wrong Sanoj, I apologize.. of course + is allowed, there are tags like c++. But you are right it doesn't let you create one. Weird. Commented Apr 3, 2010 at 9:40
  • 3
    see meta.stackexchange.com/questions/43681/… for why "++" works but "+" doesn't Commented Apr 3, 2010 at 12:38
  • Connect them with a hyphen.
    – kennytm
    Commented Apr 3, 2010 at 15:07
  • @KennyTM: I actually want a + for use in b+tree, because b-tree is something different.
    – Jonas
    Commented Apr 4, 2010 at 10:12
  • @Jonas Use something more descriptive. If you were to use b+tree when there's already a b-tree (and a few/several other tags along those lines), then people will be confused and use the wrong tag, or use both tags. Yes, you could put the information in the tag excerpt, but people commonly don't read those.
    – Makyen
    Commented Jun 13, 2021 at 23:39

4 Answers 4


b-tree is the tag for both, b-tree and b+ tree. You do not need an extra tag for it. You explain in your question that it is a b+ tree, that's sufficient.

No-one clicking with "oh, a b-tree question, I can answer this!" in mind will be scared away with "Aaaah, b+! The evil master! Run, run!" after reading the question text.

There are already several questions which do exactly that (using b-tree for b+ trees, not scaring their readers away).

  • 1
    Fair enough, this is what I ended up with and did.
    – Jonas
    Commented Apr 6, 2010 at 18:01

@Sanoj wrote:
I actually want a + for use in b+tree, because b-tree is something different

Here's a workaround:


  • this is what I recommend, if the distinction is so important. we don't allow plus in the middle of tags. Commented Jun 7, 2010 at 8:59

You can't create tags with a plus in the middle, because .. well, just look:


is that questions tagged [b] and [tree]?

Incidentally, that's why when any tag contains a plus (we only allow it at the end) you must (and our system does) delimit tags in URLs with a space.


If you're creating new tags, you're probably doing something wrong. 99% of the time or more you should be using existing tags. It's extremely rare to have a question that covers a completely new topic area.

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    I agree, but this is not an answer to my question.
    – Jonas
    Commented Apr 6, 2010 at 17:57

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