How does Safari's Reader work and when does it show up?

Safari's Reader feature is a cool little app that displays a web page as a newspaper article --- without all the distracting sidebars, comments, and ads. Sometimes it works and sometimes it doesn't, and I'm wondering how "it knows when to show up." On my personal website, one of the pages has this option. You can click the Reader button in the URL bar and it is displayed beautifully like a page in an iBook. However, none of my other web pages (on the same site) do this. I thought it had something to do with the <article> tag, but I removed that and it still works. Anyone know how this app works?

Also, does anyone know of any Chrome extensions that are just like this? Google Reader is not the same thing.

PS: From the cited Apple website:

Safari Reader

As you browse the web, Safari detects if you are on a web page with an article. Click the Reader button that appears in the Smart Address Field and an elegant view of the article appears — without any distracting content.

Not much help, is it?

Solution 1:

Safari's Reader makes use of Readability.

Readability turns any web page into a clean view for reading now or later on your computer, smartphone, or tablet.

There's this nice article about how Safari's Reader detects the text, you should consider reading.

It looks like that Safari Reader will detect a <div> or block level element that contains a header element (<h1> to <h6>), followed by a certain amount of text. The reader badge will appear when the content text (not including the header) is more than 2,000 characters.

There's a Readability extension for Chrome which you can get from here.

Solution 2:

You can take a look at its source code

Method how to obtain it is here