URLs are like street addresses for Web sites. They point your browser to the right page.

Most URLs are too long for services like Twitter. With a 140-character limit, every letter counts. URL shorteners solve this problem. But they create new problems.

URL shorteners usually make URLs less than 20 characters. For example, you would see this http://bit.ly/2ud3GL instead of this http://www.komando.com/downloads/category.aspx?id=3854. The link is about free old radio shows in case you want to check it out. These small URLs redirect to any regular URL. So, you can link to any Web site without wasting space.

But, Twitter doesn’t tell you where a shortened URL goes. It could redirect you to malicious or inappropriate sites. You’re surfing blind when you click these links.

This isn’t Twitter’s fault. In fact, it works to catch bad URLs. But you can’t be sure Twitter will block them all.

A malicious site is one that is intended to attack your computer. Criminals sometimes build these Web sites. More often, they compromise poorly protected legitimate sites.