Note: If you want to configure your subdomain manually follow the instructions in the article: https://help.short.io/en/articles/9720643-how-to-connect-my-cloudflare-subdomain-with-short-io
How to automatically connect your subdomain
Sign in to your Short.io account.
Open the User menu and click on Add domain:
In the next screen click on Add my own domain:
Enter your domain name, select the option This is domain I already use for website or blog.
Select the option that suits you best for subdomain name and click on Add domain:
In the next screen, you can click on:
Instruction: if you decide to still perform a manual connection
Configure: if you want to continue with the automatic presets
When you click on Configure, the following message appears:
Click on Confirm. You are redirected to the Cloudflare login page.
After logging in, you can review the automatic presets on your dashboard:
Click on Authorize. You are redirected again to the Short.io dashboard.
Configuring the connection takes around 15 minutes and during that time you may still see the following message:
You can click on the refresh icon until the message disappears.
When the domain becomes active, feel free to shorten links and enjoy Short.io.