Sometimes, you register a domain but you don't have a server. You may want this domain to redirect to your homepage/FB/IG or etc. However, most domain registrars do not provide this service, or this service charges. At this point, you can do URL redirecting with the github page.
First, create a new empty repo and import this repo to it.
Second, configure a CNAME record to your domain as follows:
Host: whatever you want. e.g. "www" or "@"
Target / Canonical name: your_username.github.io.
TTL: 10 min
You may also configure an A record instead of the CNAME record as follows:
Host: whatever you want. e.g. "www" or "@"
IP: 185.199.108.153
185.199.109.153
185.199.110.153
185.199.111.153
TTL: 10 min
Third, change the contents of the CNAME file in the repo to your domain.
Fourth, replace the URL is the index.html to whatever your want.
There is also a Chinese version for this repo.