It is not necessary to register a new domain name for shortening links if you own one that works properly. Create a subdomain using a domain you already own.
1. Go to your Hostinger account.
2. Click on the arrow icon next to your domain.
3. Click on "DNS / Nameservers" tab.
4. In the section 'Manage DNS records' enter the following values:
Type - CNAME; Name - your subdomain; Target - cname.short.io; TTL - 3600
Click 'Add Record'.
5. Go to your Short.io account.
6. Open the User menu and choose "Add a domain".
7. Choose the option — Add my own domain
8. Specify a domain and choose the second option. Then choose the subdomain from the list or choose 'Custom subdomain' and type in your value
9. Go to the Short.io domain settings to check if the domain is active. Wait a few hours and refresh a domain status in Short.io domain settings.
10. After the domain is active, feel free to shorten links and enjoy Short.io.