What makes a "friendly URL"?

Question

I've read a great deal of discussion recently (both on this site and elsewhere) about "friendly URLs" but I'm not sure what exactly makes a URL "friendly" and why we really even care (up to a certain point). Illustration:

The following is an example of a URL that would be held up by the majority of current web developers as "friendly":

www.myblog.com/posts/123/this-is-the-name-of-my-blog-post

Whereas this would be considered "unfriendly" (i.e. bad, Neanderthal, ignorant, stupid):

www.myblog.com/posts.aspx?id=123

My questions:

• Doesn't the "friendly" URL contain duplicate identifying information about the blog post in question? In other words, once you have the id (123) of the post, why do you need the title? Wouldn't this be a violation of the "don't repeat yourself" mantra?
• What difference does the form of a URL make as far as users are concerned? Do users ever actually type full URLs by hand (other than the TLD, of course)? Do users ever look to the URL of a page to determine what the page is about? Why do we need the title of the blog post in the URL? Isn't that what the page's <title> tag and content are for?
• I often hear SEO as a reason why the "friendly" URL form is preferred. Why does a search engine spider care about the URL? Aren't they just automated pieces of software that crawl pages (and the links to other pages that are contained within them)? If search engines were written like other software components (e.g. database access components), the URL would just be a meaningless identifier (similar to a rowguid in a relational database) to them. If I were designing a database schema with something like the "friendly" URL above as a table's primary key, I would (quite correctly) get chewed out.

I said earlier "up to a point" because obviously, URLs can get out of hand. Here is an actual URL from Amazon.com that I don't think anyone in their right mind would consider "friendly":

http://www.amazon.com/Bissell-Kitchen-Housewares/b/ref=amb_link_5001972_17?ie=UTF8&node=694500&pf_rd_m=ATVPDKIKX0DER&pf_rd_s=gp-center-5&pf_rd_r=1ZXNJFE0CCFFDH4B9HGH&pf_rd_t=101&pf_rd_p=405478901&pf_rd_i=510080

Answer 1

Tim Berners-Lee (the architect of the WWW) wrote a great article about this subject about 10 years ago.

• Your example is a bad URL -- but not just because it has both an id and a "slug" (the abbreviated, hyphenated form of the page title). Putting the page title into your URL is problematic in the long term. Content will change over time. If you ever change the title of that blog post, you'll be forced to choose between keeping the old URL, or changing the URL to match the new title. Changing the URL will break any previous links to that page; and not changing it means you'll have a URL that doesn't match the page. Neither is good for the user. Better to just go with www.myblog.com/posts/123.

• Users often do need to type a URL, but more importantly, sometimes they'll also edit existing URLs to find other pages in your site. Thus, it's often good to have discoverable URLs. For example, if I want to see post #124, I could easily look at the current URL and figure that the URL for the page I want to see is www.myblog.com/posts/124. That's a level of user-friendliness that can be a big help to people trying to find what they're looking for. Including other information (like the subject of the post) can make this impossible -- so it reduces my exploration options.

• Forget about SEO. Search engine technology has been reducing the effectiveness of SEO hacks for some time. Good content is still king -- and in the long run, you won't be able to game the system.