I found this Superuser question had the 'software-rec' tag twice:
Best/Preferred software for photography (revisions).

How was the second instance allowed to be tagged?
I expected the duplicate tag to be automatically cleared/dissolved when Lance saved the edit.

Removed the duplicate tag (see the revisions link).
But, is this expected behavior?

If it is allowed to repeat a tag -- why?

If as random says, a global conversion caused the duplication of this tag,
I'd still kind-of expect the conversion to be implemented to check for such duplicates
(caused by it).

I would also be surprised to find someone choose to shorten a tag and
did not delete the older longer form (for the conversion to cause a duplicate later).


3 Answers 3


I've added a moderator function which deduplicates all current question tags, and all post history tag entries.

So the next time there's a duplicate tag problem, just flag one of them for moderator attention and we'll run the tag deduplicator page.


[software-rec] used to be [software-recommendation] so it's possible that when Lance went to retag, it was already sporting the latter.

And then some global merge/rename (of the latter style to the former) left the question with the case of duplicate tags.

  • Hmm, so maybe Lance saw the longer form, added the shorter form and then the global conversion shortened the longer one to make a duplicate.
    – nik
    Oct 13, 2009 at 5:18

Not really valid - but it happens as an unwanted side-effect of retags (see tags on this question).

I'm hopeful Jeff/team will add a de-dup script (if it doesn't already exist). I'll keep an eye on this question and see if it fixes itself...

Basically, from what I understand from Jeff, the tag-merge script is a simple UPDATE command that changes the ids only - it doesn't checks for dups because of the performance cost. But I'm thinking a scheduled job (perhaps once a day) should be reasonable...

  • Is this automatically cleaned in some way? Or do we have to manually retag everything?
    – alex
    Oct 13, 2009 at 6:39
  • Thanks, this is what i would expect too.
    – nik
    Oct 13, 2009 at 10:48
  • @alex: we have to manually retag everything.
    – perbert
    Oct 13, 2009 at 17:23

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