Before you click that shortened URL, know the (harsh) facts.

Short links, shortened URLs, tiny URLs: Whatever you call them, they’re everywhere. More than 200 link-shortening services—including the popular Bitly, TinyURL, Google URL Shortener, and Twitter’s link service—turn millions of long, unwieldy URLs into short, spiffy links.

The convenience factor is clear. Sometimes you don’t want a four-line link filled with crazy characters cluttering your email or Facebook post. Platforms like Twitter have rigid character counts ...