As far as I know, moderators can cancel tag synonyms and such things happen occasionally. (I've seen some threads about removal of tag synonyms here on meta.SE.)

How will the questions be tagged after the removal of the synonym? We have many questions tagged (master-tag). Some of them might have been tagged by (slave-tag) at the time when the synonym was created. Some of them might be tagged (master-tag), but they got this tag after a user explicitly typed (slave-tag) when entering the tags.1 After removing the synonym, do all question keep the (master-tag)? Or do some of the questions get the (slave-tag)? (For example, the two types of questions mentioned before seem like a reasonable candidates.)

An additional question: Does it make a difference whether the two tags have been merged2 or only synonymized?

Originally I have asked this at a local meta but this is probably a more appropriate place (and with a better chance to get an answer).

1Number of such posts is shown in the list of tag-synonyms.

2From what I have read here it seems that merging is independent from creating a synonym. But it is sometimes done when a tag-synonym is created. Based on the answer to the following post, it seems that there might be a difference: Need a rollback/undo for tag synonym merging.

1 Answer 1


Removing a tag synonym essentially just tells the system to no longer consider the two tags the same (with as the master).

Within the database no changes are made to posts. Questions tagged will still have the tag . Similarly, questions tagged will still have that tag. Only now these questions will be displayed as such. Here it is important to remember that when the synonym is introduced no changes are made to questions: they retain their given tags. The system is told the treat as if it were . In particular,

  • a question tagged will be displayed — and otherwise act — as though it was tagged , and
  • when a user tries to explicitly tag a question , it is instead given the tag.

This means that questions tagged before the synonym was introduced (and not edited while the synonym was in place) will have that tag after the synonym is removed. However no question created while the synonym was in place will be tagged .

Merging into is the (silent) process by which the tags of questions are wholesale altered. Here, will be removed from all questions and replaced by (provided they don't already have that tag).

If is also made a synonym of , then when this synonym is removed no question will have the tag.

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