This website has been known to distribute spyware." TinyURL countered this problem by offering an option to view a link's destination before using a shortened URL. Twitter will use this to make your timeline better. Twitter will use this to make your timeline better.
When clicking the link, Sailthru tracks the click and quickly redirects the user to the applicable page on your site, example.com/item/123. It's also important to note that some countries only allow registrations on what's call the third level — .co.uk for example.
This should not contain information already in the campaign name or medium fields. Another operational limitation of URL shortening services is that browsers do not resend POST bodies when a redirect is encountered.
Many sites that accept user-submitted content block links, however, to certain domains in order to cut down on spam, and for this reason, known URL redirection services are often themselves added to spam blacklists. Use an online search tool: One great tool for coming up with good domains for URL shorteners is Domai.nr, which lets you type in a full company name and the site suggests variations of it using numerous alternate extensions and other methods mentioned here and even links you to where you can purchase the domains (this is especially handy for country TLDs). For example, if you send out weekly newsletters, this might be "newsletter". At that time, Google will completely disable the URL shortener and all associated data will be lost.
When developing your application, however, feel free to use your preferred HTTP, JSON, and OAuth libraries. Twitter will use this to make your timeline better. See if you are using Classic Analytics (ga.js) or Universal Analytics (analytics.js).