https://showmanga.blog.fc2.com/blog-entry-626.html

The URL shortener 4h at 4h.net can be used to create free short URLs (Uniform Resource Locators) or web page addresses that can be easily shared, tweeted, or emailed to your friends. Enter a long URL, and you will get a short URL you can use in its place
4h works as a conductor or proxy for a long URL. The shortener links the longer URL to the shortened version