Smart Moves in URL Shorteners

It’s no secret that virtually every popular (and non popular) site on the web has a URL shortener. What if that URL shortener ceases to exist? This has been discussed more times than I can enumerate I’m sure, but I’d really just like to pose an observation that seems like a good idea.

We’ve been playing around a bit with FreeBase at work. It’s going to “solve” all of the data problems we have for a new product. In reality, it brings up way more, but bare with me.

Revolution OS, which should be in every hacker’s Netflix queue if not consumed already, on FreeBase, has many links attached to it. Now, regardless of what you do with these links, it might make sense in the case of a film to extract the Netflix link to pull structured information from that service as well. The astute reader has already seen where I’m going with this, and will point out that the link is already expanded, but bare with me–I wanted to plug a favorite documentary (even if it is aging).

Notice the “movi.es” link. “movi.es”, as it turns out, is the domain that Netflix uses for shortened URLs. The short link for Revolution OS is http://movi.es/ApRqW. Following that link, of course, will redirect you to http://movies.netflix.com/Movie/Revolution%20OS/60025132, which contains a bit of interesting information in it–the unique id of the movie on Netflix (in this case 60025132).

What’s smart is that Netflix uses a predictable scheme for these mappings. Many other services do this. And, if you search DuckDuckGo (or your favorite search engine) for how to build a URL shortener, you’re likely to find the similar methods illustrated. In fact, Netflix just uses Base 62, though with an unnecessary twist.

The twist is that they take the id (e.g. 60025132), prepend 1 to it (e.g. 160025132) and encode the result. It’s simple and effective, but unfortunately not immediately obvious (it took about 20 minutes of trial, error and some Python to nail this down with a coworker).

It’s obvious, and simple that will save immense effort in preserving the world wide web. We’ll still need projects like 301works in the fight against Link rot–mostly for general purpose shorteners like bitly.

But, for specialized shorteners like “movi.es”–well, don’t over engineer it. Do something simple, something predictable. Or, better yet, don’t make me guess! Just tell me how to reverse them. That way I don’t have to crawl your site unnecessarily.

— 2012-03-13