In one of those instances of convergent online evolution, the subject of URL shorteners has been popping up a lot lately. You know; TinyURL,,, and the like. I suspect a lot of this talk was prompted by the launch of the DiggBar and its accompanying short URL service that serves up your content in an iframe—time to break out that frame-busting JavaScript you haven’t needed for years.

David Weiss writes about the security implications of URL shortening services. Meanwhile, Joshua Schachter talks about the danger of link rot:

The worst problem is that shortening services add another layer of indirection to an already creaky system. A regular hyperlink implicates a browser, its DNS resolver, the publisher’s DNS server, and the publisher’s website. With a shortening service, you’re adding something that acts like a third DNS resolver, except one that is assembled out of unvetted PHP and MySQL, without the benevolent oversight of luminaries like Dan Kaminsky and St. Postel.

Dave Winer agrees:

We need to prepare for the day when N of the URL shorteners go out of business. When that happens a large part of the web will die. It will not be a good day.

Take the case of Twitter. Messages on Twitter are archived and addressable. If those messages contain links, they are shortened using TinyURL. If TinyURL were to disappear, it would leave a swamp of unresolved endpoints. Jason Kottke has a modest proposal:

In cases where shortening is necessary, Twitter should automatically use a shortener of their own. That way, users know what they’re getting and as long as Twitter is around, those links stay alive.

That would definitely work for that particular case. Of course Twitter could disappear, taking its archive of messages with it, but that’s a different situation. The loss of shortened URLs would be tightly coupled to the loss of the original messages.

But Twitter is just one example. What about the rest of us? Right now, if someone wants to pass around a shortened version of one of my URLs, they could use any one of the many URL shortening services out there. The result is potentially a score of different short URLs leading to the same endpoint. If some of those services disappear, link rot spreads.

Ideally, I should be able to specify a desired short URL for my content. This is something that Dopplr is already doing with its domain.

Kellan says that they’re also putting together a URL shortener over at Flickr. He’s thinking about how to specify a short URL for a document: some way of specifying here’s the short URL for this page in the same way that we can specify here’s the stylesheet for this page or here’s the RSS feed for this page.

The rel attribute is used for stylesheets and RSS feeds so perhaps that’s the way to go. Something along the lines of rel="alternate shorter" in the same way that we can point to an alternate stylesheet with rel="alternate stylesheet". But in this case, we’re actually pointing to the same resource but with a different URL. So maybe something like rel="alternate shorter self" would be more accurate. Heck, we could probably throw the bookmark value in there too: rel="alternate shorter self bookmark".

Kevin pointed out on Twitter that rev (reverse relationship) would be more suitable than rel.

Google introduced rel="canonical" recently. It’s a way of pointing from an alternate URL back to the canonical URL of the current document: the relationship of the linked document to the current document is “canonical”.

If you’re linking from the canonical URL to an alternate URL (like, say, a shortened URL), you could use rev="canonical": the relationship of the current document to the linked document is “canonical”.

This certainly seems to be the more semantically correct way of pointing to a shortened URL. Alas, rev is a beleaguered little emo attribute: no-one understands it. At least, that’s the claim of the HTML5 community, who plan to drop it completely.

Personally, I share Paul’s intuitions:

HTML is a living language and the HTML5 WG should behave more like the OED rather than the French Government.

So if enough of us publish documents using ARIA roles, accesskey or rev attributes, they will not go gentle into that good night.

Should the idea of distributed, rather than centralised, URL shortening take off, I can imagine a situation where short URL auto-discovery is as commonplace as . So if I paste a link into a microblogging site like Twitter, or choose to “Mail this page” from my browser, then the website or mail client could check the head of the document for a preferred short URL. It’s a little bit like OpenID delegation: I could either create my own URL shortening service or specify a provider I trust.

Josh is already playing around with shortened links back to posts on his blog. Now suppose he also specifies the short URL (using rev="canonical") on those blog posts…

Update: Kellan has now implemented rev="canonical" auto-discovery.

Update 2: …and Dopplr have duly implemented rev="canonical" which works a treat with Kellan’s auto-discovery tool. Here’s an example.

Update 3: This just keeps getting better. Now there’s a blog devoted to rev="canonical" which has already documented not one, but two Wordpress plugins.

Have you published a response to this? :

Previously on this day

14 years ago I wrote Bootcampilicious

Holy shit!

15 years ago I wrote Feed me

Molly’s been busy lately. Not only has she been interviewing the father of CSS, she’s also found time to put together a table of syndication link locations.

15 years ago I wrote Buying music

Mark Cuban believes the countdown to the extinction of CDs is about to begin. He bases this on personal experience:

17 years ago I wrote One Cool Cucumber

Bleeding ears, stiff upper lip… it must be John Simpson:

18 years ago I wrote Paris in Spring

I’m making a flying visit to Paris this weekend.

18 years ago I wrote Web Designer Builds Home out of Flash

It’s funny because it’s true: