I have to believe this already exists but my search foo sucks so I threw together a small app/script to retag questions for helping me fix some bad tags.

For example you can search for tags with [tag:foo] and [tag:bar] then say remove [tag:bar] and add [tag:moo]. I have not automated it yet (not sure I will). It just gives the top 30 questions and has a button to manually apply the change one question at a time.

It seems to be working

## How to use

* Go to https://greggman.github.io/fixallthetags/
* Login to Stack Overflow 
* Type 2 or more tags: eg. `html canvas`
* Enter tags to remove: eg `canvas` (a meaningless tag)
* Enter tags to add: eg `html5-canvas` (the correct tag)

The questions should show old tags on the left, new tags on the right. If you're feeling lucky/dangerous click `fix` for a question and it should update the tags. Ctrl/Cmd click the link to the question to open it up in Stack Overflow in a new tab and just below the question you should see your user icon and an `edited` link. Click that link to see a diff. It should only show that you changed the tags. If you see anything else please [submit a pull request](https://github.com/greggman/fixallthetags) or [file an issue](https://github.com/greggman/fixallthetags/issues).

Note that one issue it does not grab the latest version of the question before submitting. It's using the version of the question as it was when the search was made. I'll fix that in the near future.