It's probably just a short URL is a heuristic for an important site. www.site.com/section is probably more important than www.site.com/section/subsection/detail/page/5/comments. A good move for the crawler - don't get distracted by "deep" pages - try and stick to high level ones first.

Edit: this would also encourage webmasters to use short URLs, which benefits users by being easier to remember, too.

How well-known is this to webmasters? If it's not well-known I cannot see how the second part could be. But the first could very much be true, and is what I would've surmised.

I don't agree with the last point; seems like it would encourage things like foo.com/1hu83FG2 or lead to excessive abbreviation.

If I remember correctly, your page ranks better in Google if the search terms are in the URL (even more so if they are in the hostname).

Well, it's just a heuristic. Also, would you consider that level of abbreviation for your own site instead of descriptive names? You do want users to be able to remember URLs if at all possible...

There is probably some highly non-obvious reason that sorting your queue of URLs by length is optimal, which was arrived at after a lot of modelling and testing.

We're unlikely to ever know the answer unless someone from google explains it to us.

Thinking about it more, its probably just a breadth-first search. Duh.

Breadth-first search means crawling all of the links on the page and adding all of the links on the child pages to the queue at once rather than drilling down on one link-path first before moving to the other links on the first page. There's probably some highly non-obvious reason for crawling by url length.

The thing is, the deeper you are, the longer are the urls, so if you do a breadth first search, you are more likely to visit short urls first.

The site adheres to a strict url structure. /state/city/id/schoolname - entering from the homepage, the only way to crawl the site 1 level at a time would be crawling the shortest urls first. this structure is also emphasised in the breadcrumbs on every page, the shortest urls are also the ones with the most internal links.

why would you crawl the site in any other way?

If you look at a particular city page you will notice that the cities are in alphabetical order, however google bot still crawls by length of url...

"why would you crawl the site any other way?"

I could see crawling pages most likely to have changed first as those pages would most likely lead to fresh content.

I did a more scientific analysis of the googlebot requests in the provided log (graph! http://i.imgur.com/uMoUT.png) and it definitely looks like it is taking shortest urls first. Anyone else with a large site want to check as well for further data?

Thanks for the graph, I've added it to the blog page

That's probably because short urls usually tend to be static pages while long ones tend to be dynamically generated content.

His entire site that he observed this behavior on is static.

But Google doesn't know that.

I imagine that in these specific case is because longer URLs represent deeper pages on the site that are less "important" (in terms of internal incoming links and pagerank) than the shorter ones. It doesn't seem logical that google order the URLs by length and then crawl them in that order; probably the URL length can be a factor that the bot takes into account, but not the only one in the manner this article suggest :)

Anyway, good point, that deserves more testing to extract some conclussions

A poor mans PageRank algorithm, assuming nothing else, would assign a higher PageRank to shorter site links on a page. Presumably the crawler visits pages with a higher PR first.

Pagerank determine crawls rate amongst other things. I find it is also likely that short URLs (especially in the case of a directory-type site) are seen first by the spider and that this order is respected by the crawler (FIFO).

You can also ask in #seo on irc.freenode.net I know there are knowledgable SEO people in there who might be able to provide you with a decent answer.

The question that I have is whether this is a relative behavior (i.e. whether, for a given domain 'domain.com' Google prioritizes domain.com/short-url over domain.com/longer/url.html) or a global one (i.e. prioritizing short.com/url over very-long-domain.com/nested/pages/hierarchy.html, all else equal).

I can definitely see the local/relative effects being a natural consequence of prioritizing by pagerank, but the global part sounds more like a separate signal.

Does anyone have insights?

I noticed this behavior also when I was following Googlebot's crawl of my old pages after I had done a redesign.

it's not because of sitemap or because of url structure or because of dynamic content.

Mine were blog articles in the same format. This is how it was crawled:

sitename.com/year/mo/day/stub

sitename.com/year/mo/day/stub-one

sitename.com/year/mo/day/stub-one-two

sitename.com/year/mo/day/stub-one-two-three

sitename.com/year/mo/day/stub-one-two-three-four

It starts at the top of your sitemap - which are likely shorter URLs

Maybe because that's how they are sorted in the hashtable/database they use to queue urls? Or maybe because they want to index the shortest pages first, so that they are processed before any duplicates with longer urls (i.e. get /articles/ before /articles/index.php)

I suspect you're on the right track with your first guess.

Most people posting here are looking for some sort of deep meaning in this when IMO it is more likely just due to a localized side-effect of doing something such as storing the urls in a trie-like structure and then iterating over it breadth-first.