question about short url service

Hello I know that some short url service are like 301 and some not.
How can I understand when a short url service is 301?
thanks
Arianna

Right click anywhere on any page and click "Inspect". This will open up firebug. Go to the network tab. In Chrome click the red button to make sure requests are not discarded when you're redirected.

From there, open up the link and you'll see if the status code is 301.