EZ Git.io is a tool to request custom (vanity) git.io shortlinks for any GitHub URL. This was previously done using curl for PHP, but due to my recent discovery of the no-cors option in fetch, it's now done client-side with Javascript!
Yes, you can do this with command line curl without this tool; for instructions on that, check this blog post.
Click Here, it works right in your browser.
Can I create multiple git.io shortlinks for a GitHub page?
No, you can only create one shortlink per page. I recommend adding an empty query (a question mark character) after the URL if you want to create multiple shortlinks to the same page (i.e if a shortlink has been created for https://github.com/, try shortening it as https://github.com/?). Thanks to this Stack Overflow post for this good advice.
I made a mistake! Can I delete a shortened URL?
I have not found any way to do this from the user's end. I would try contacting GitHub to see if they can delete a shortlink for you. If you know something I don't, though, let me know!
Can I create a git.io shortlink for X website?
If X website is not a GitHub-owned URL, you cannot shorten it with git.io.
Can I use an existing shortlink?
Nope, see above about deleting a shortened URL.
I think I've done everything correctly, but still no shortlink!
Check to make sure that you have Javascript enabled and that the POST request for a new shortlink is actually going through using Chrome Devtools or some equivalent. If you still aren't getting a shortlink, there's a bigger problem (GitHub changing the git.io API, etc.) so please file an issue here.
Big thanks to that blog post I mentioned earlier for getting me started with git.io.