Twitter recently announced its own “t.co” URL shortener — and besides being a handy gadget for users, the service is a valuable resource for marketers, writes Alistair Croll. Most digital marketers rely on cookie-based tracking to keep tabs on their audience, but that doesn’t work well for social-media campaigns designed to be shared across a range of platforms and applications. That’s where t.co comes in: Since Twitter controls the way content is mapped onto shortened URLs, it can produce analytic data and tracking even when content is shared across many platforms. “This is why short URLs are so important. URLs survive the share,” Croll writes.