Helpers, Plug-ins and MIME Types 

3/4/98 
J. L. Mohler 

As you look at the wide range of multimedia elements that can be distributed on the web, you’ll notice that they can be included in web pages in a variety of ways. Originally the browser could only interpret HTML code and plain GIF and JPEG graphics. Yet, as what we have wanted to do has gotten more complex, special capabilities have been added through add-on programs which allow multimedia elements to be embedded directly within HTML pages. 

As you look at the brief history of the web browser, you’ll see the beginnings of web multimedia capabilities found in the use of helper applications. Helper applications are applications that are external to the browser (often times created by a separate company) and are executed as certain media elements are encountered or downloaded from the web. Even though the use of helper applications is decreasing, realize that many sites and end-users still depend upon them for playback of content. 

For example, one of the first ways of utilizing digital video movies, such as QuickTime movies, was to utilize the QuickTime movie player application. In this scenario, when the browser encountered a page with a QuickTime video file, the user was required to click a hotlink, which would then download the movie. Once the movie was downloaded, the browser would open an external application, Apple’s QuickTime Movie Player, and play the movie. Any file that was foreign to the browser (anything other than HTML, GIF, or JPEG) required an external helper application. 

Enter Multipurpose Internet Mail Extensions 
The browser derives all its application associations, the information that tells it how to view files (based on the three-character DOS file extensions) from an information list called Multipurpose Internet Mail Extensions (MIME). This list must be defined in the browser as well as on the server used for distributing web files. 

The MIME list defines several important pieces of information for the browser concerning any given file type. It includes: 

  • The application type, such as text or image 
  • The application sub-type, such as plain or jpeg 
  • The three letter extension for the file such as .txt or .jpg 
  • Information on what to do with the file. Options include View in Browser, Save to Disk, Prompt User, and Open Application. 
Using the MIME entry information, the browser is able to look at the three-letter extension and then determine whether to try to view the downloaded file in the browser, save it to disk, or open it into another application (a helper application). 

Moving up the food chain: Plugins
Even though helper-based multimedia was the first means of utilizing multimedia elements on the web, many companies recognized the need to be able to directly integrate multimedia into the web page, rather than requiring an external application for viewing those elements. This lead to the advent of plug-ins that could be installed on the client machine that assisted the browser in interpreting multimedia elements. These plugin-based multimedia elements, such as Shockwave, allow any range of media elements to be included on web pages. 

Realize that certain media elements, such as digital video, animations, or digitized sound, can actually utilize either plug-in technologies or helper applications. Depending on how the user machine is configured (i.e., what MIME associations are established) will determine whether a helper or plug-in is used. Because of this, you may want to specify the “advantageous” method of viewing pages that have such elements for your audience. 

Aside from helper applications and plugin technologies, I must also note that many of the browsers used to surf the web are enabling multimedia technologies themselves. For example, a GIF animation is recognized by most browsers as is the inclusion of sound elements embedded into web pages using the BGSOUND attribute of the <BODY> tag. Over time we’ll probably see more multimedia attributes directly supported by the browser, which will make setting up a web browsing environment easier. But for now most of the complex multimedia capabilities, such as highlighting buttons or multimedia presentations are a result of add-on and external programs more than they are of the browser.