Plug-ins

• Needed for certain types of files that are downloaded, especially multimedia files. Browsers themselves handle only the display of a few kinds of files: plain text, hypertext, and some graphics (.gif, .jpeg, .xbm).
• Plugins display other file-types within the browser window, e.g. the .png graphics format needs a plugin such as Quicktime3; Shockwave and Flash animations need Macromedia's plugins.
• Work specifically inside of Netscape or other browsers, such as Opera. Microsoft Internet Explorer has a different plugin architecture than Netscape, needs its own plugins.
• Examples:
  • Sounds (.wav or .ra files) -- check out Beatnik and RealPlayer
  • Video files (.avi) and Quicktime (.mov) -- Quicktime3.0 does it all
  • Acrobat (.pdf)
• Use Help-> About Plug-ins to see what plugins you have installed. You can also click on the link at the top of the resulting page to go to Netscape's plug-in repository with tons of useful plug-ins (can be very busy)
• Or go to browsers.com for latest plug-ins
• Plugins usually are free to gain wide acceptance of a new filetype; the authoring applications can be quite expensive.
• If several plugins can handle the same type of file, the one that was installed last will take precedence.

Helper Applications

• Different from plug-ins as they are full applications already on a user's computer. While a plugin opens the file inside the browser window, a helper application opens a separate application window.
• In Netscape, you can set these applications to launch when a file of a certain type is encountered, e.g.
  • .doc can open Microsoft Word
  • .wb3 can open Quattro Pro spreadsheet
• In Netscape 4.x, you can simply choose an application when you are trying to download a file-type Netscape doesn't know about. You will be offered the choice to save the file to disk, or to browse for an application to use for files of this type. In Navigator 3, a new helper application can be added at the Helper tab under the Options-> General Preferences menu. In general, Netscape will use the application associated in Windows with this filetype. A list of associations is available in Edit-> Preferences-> Navigator-> Applications.
• However, what really triggers a plugin or helper application is not the file extension, but the file's MIME-type. MIME is a convention for encoding files of any type, e.g. for attaching them to mail-messages. On the WWW, the server has a list of MIME-types it knows about, and will pass the file's MIME-type to the browser, which calls up the right plugin to handle this type. If the server does not know e.g. what a .wpd extension means (it is the extension of WordPerfect files since version 6), the browser cannot properly handle those files, because it is never told that this is a file of MIME-type application/wordperfect5.1 - bad luck! In general, if your browser chokes on files of a specific type from a specific server, it may be useful to contact that server's administrator and have the MIME table checked.
• Help with MIME types (if necessary) and a list of them