Trigger Build On Tag?

I was wondering if it was possible to trigger a Travis build when a git tag is pushed up.

I’d like to generate a special behavior once we have tagged a build.

Any documentation that I should look at would be great!!

and tag is available

Heres the jobs section on one of my projects. It does tests on all pushes, but only does the deploy stage if its a tag, and the tag looks like v<NUMBER>

    - stage: test
      script: bundle exec rake test
    - stage: deploy
      if: tag =~ ^v[0-9]+$
      script: bundle exec rake compile:all deploy

Building tags is enabled whenever “build pushed branches” is enabled – unless you disabled it with conditions.
Cannot say if that’s the case without seeing any links to your repo and/or builds.