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MIME Types

ActiveX Objects

— ActiveX objects are everywhere in Internet Explorer. You can use them from

JavaScript and you can embed them in Web pages. Although not technically a plugin, because

ActiveX support exists in Internet Explorer itself, ActiveX objects are embedded into a Web page

the same way as other plugins.

Macromedia Shockwave

— Before there was Flash, there was Shockwave. Shockwave plays

files created in Macromedia Director, a multimedia programming environment allowing devel-

opers to create interactive demos, games, and other advanced content. Although not as popular

since Flash gained notoriety, Shockwave is still available on both Windows and MacOS.

MIME Types

When talking about plugins, the concept of MIME types is central. MIME stands for Multipurpose

Internet Mail Extension, a simple text string originally designed to determine the format of e-mail

attachments. From that humble beginning, MIME types (also called content types) have grown into the

de facto standard for identifying file formats on the Internet.

Each MIME type is made up of a media type and a subtype. The media type can be application, image,

audio, video, text, message, model, and multipart. The subtype is typically a more unique identifier,

specifying anything from the type of compression scheme used to the file extension. The media type

and subtype are separated by a forward-slash (/), such as

text/css

, which tells the browser (or other

Internet application) that the file is plain text and is also a CSS style sheet. Browser plugins work by

mapping themselves to specific MIME types, telling the browser that when this specific type of file has

to be handled, it should be done by the plugin.

Naturally, several MIME types are handled by the browser itself, such as

text/javascript

(JavaScript

files),

text/css

(CSS style sheets),

image/gif

(GIF-encoded images),

image/jpeg

(JPEG-encoded

images),

text/xml

(XML files), and

text/html

(HTML files). Many others, however, are handled by

plugins.

Embedding Plugins

To embed a plugin into a Web page, HTML offers the

element. At the very least,

requires four attributes:

type

— The MIME type of the file or object being embedded

data

— The URL of a file to load into the object

width

— The horizontal space the object should take up in the page

height

— The vertical space the object should take up in the page

The browser internally equates the MIME type of a file with a particular plugin, so setting the

type

attribute is enough to tell the browser which plugin to load. For example, the content type for a Flash file

application/x-shockwave-flash

, so the following code is all you need to embed a Flash movie:

width=”100” height=”100”></object>

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Interacting with Plugins

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