You do not need to register a new domain name for shortening links if you own one that works properly.
In case you already have a website on this domain, create a subdomain to shorten links with it. The advantages are cost saving and brand recognition.
Before adding your subdomain to Short.io, you need to follow some activation steps in order to connect the subdomain with Short.io and then use it for link shortening.
We have compiled a brief list of articles with various domain registrars to assist you in setting up your subdomain.
And if your registrar is not on the list, consider the following
General instructions
Sign in to your domain registrar's page.
Select the subdomain you want to connect with Short.io.
Open the DNS settings.
Add one CNAME record with following details:
Host: <your-subdomain-name>
Type: CNAME
Target: cname.short.io
Save the new settings.
The next step is to add the subdomain to Short.io according to the instructions in this article: https://help.short.io/en/articles/10678028-how-can-i-add-my-subdomain-to-short-io
In case of any questions, feel free to contact the Short.io support.