Knowledge Base Overview

A pretty legitimate question which is not easy to answer, i.e. in one word or a short sentence. It will require even more than one paragraph.

What is a media type

To answer this question we have to understand what kind of devices or better yet applications work with HTML documents.

What is a user agent

Every application (not device)—or media—which is capable of rendering a web page (an HTML document) is a user-agent.

Got it? No? Lets read this sentence once more but backwards kinda. A user agent is capable of rendering a web page. In other words, the piece of software that understands HTML and interprets the document is called a user-agent.

The user-agent and piece of software we are most familiar with is the web browser. However there are other applications that work with HTML document. Just think about a document for people who are blind which basically reads the document to a person.

Different user-agent characteristics

The various user-agents can be grouped according to some common characteristics into a media group.

Now back to our media type. Although a media type seems to define a device it actually defines the characteristics for CSS, cascading style sheets. However, a media type has a relationship with media groups which in return links a certain user-agent to a media type.

List of media groups and types

The media types are specified by W3C and are part of the CSS2 specification. The specification has the list with all the available media types.

Who defines the media type?

Good question. There is no clear definition which means the producer of a user-agents is free to decide in which media group the device fits. From there a media type can be selected and assigned.

Media Type: screen

Many will assume that a desktop monitor is a user agent and screen is the media type for the monitor—which is false. You may also assume that when we print a page the printer is the user-agent and the media type is print. False again! It is the browser in either case! As stated earlier a user agent must be able to render a HTML document. A monitor knows nothing about HTML and so does the printer. Only the browser knows how to render a HTML document.

The browser is the user-agent and fits into the continuous and page media groups. A web browser in your desktop computer and for viewing handles continuous media and should identify itself as media type screen. If a user decides to print the web page the browser handles a page media. The browser now fits into the page media group and identifies itself as media type print.

What about handheld

So, what about the iPhone or Android phone, our smartphone devices we hold in our hands?

Looking at all the media types we see a type named handheld. Is a smartphone a handheld device? I would say so, yes. However, looking at the definition above it is not the physical device who defines the media type, it is the user-agent. With our new smartphones the user-agent would be a browser.

Beginning with the iPhone and the Safari browser up to Android phones with Firefox, Opera and whatever is available, they all have decided to identify themselves as media type screen.