Add this to your bookmarks or drag it to your bookmarks bar to quickly access shortening functions: Shorten
This bookmarklet takes the page URL and title and opens a new tab, where you can fill out a CAPTCHA. If you have selected text before using the bookmarklet, that will be used as the keyword.
Support for bookmarklets on mobile varies. For example, they work on Chrome for Android but you have to add and sync them from your desktop.