For users working with repositories, Bitbucket supports Git 1.7 or later and Mercurial version 2.1 or later. If you are a developer working with Mercurial, we do not support the LargeFiles extension. To see what technology we currently use to run Bitbucket, scroll to the Bitbucket footer. The footer appears at the very bottom of each page on our site.
You are free to try and use any version of Git or Mercurial you want with Bitbucket. If, for example, your IDE limits you to a particular version of Git or Mercurial, use the version your IDE supports. Make sure you state the DVCS versions you are using if you have to log a support request, comment on a blog, or post to a Bitbucket discussion list.