# Presentation: 512608

## Recommended File Formats for WWW

- A guide for Webmasters

## Introduction

- File formats?  What file formats?
- Isn’t MIME a guy in white make-up?
- Viewers, external applications, or helper applications
- Images, photos, sound, video, documents
- Non-traditional viewers

## File formats?  What file formats?

- HTML allows links from a document to other files in any format, but which file format(s) should you, as a Webmaster, use?
- Users will access your documents from PC, Mac, UNIX, X, Amiga, NeXT, VMS, VM, America On-line, BIX, Prodigy, dumb terminal, *et cetera*
- Netscape, Mosaic, MacWeb, WinWeb, Cello, Lynx, MS-Word, GWHIS, Galahad, SlipKnot, Agora, OmniWeb, Samba, MidasWWW, ViolaWWW, Chimera, Arena, Albert, *et cetera*

## Isn’t MIME a guy in white make-up?

- MIME stands for Multimedia Internet Mail Extensions, RFC-1341
- MIME redefined the format of RFC-822 e-mail message bodies to allow multi-part textual and non-textual bodies to be represented and exchanged without loss of information
- Each file sent from a WWW server to a WWW client has a MIME Content-type
- WWW clients can't handle some of these file types internally

## Viewers, external applications, or helper applications

- The WWW model gets over the frustrating incompatibilities of data format between suppliers and reader by allowing negotiation of format between a smart browser and a smart server.
- Data format information is primarily conveyed by MIME content-type; secondarily by file extension
- Clients are configured to launch viewers which understand the data formats
- Many free viewers are available

## Images

- In-line Images
- Images which appear inside a WWW document (no external viewer)
- Client support is determining factor
- Recommendation:GIF 89a (interlaced)
- Keep color count low!

- External Images
- For most computer-generate graphics, line art or other images with relatively few colors or large areas of homogenous color
- Compression is determining factor
- Recommendation:GIF 89a (interlaced)

## Photos

- Photographs typically have many more colors than images
- Photographs are best viewed as external images to allow better manipulation tools
- Compression is determining factor
- Recommendation: JPEG
- A small “thumb-nail” image (small color count) can be an anchor pointing to a large, full-color photo

## Sound Bites

- Digitized audio clips
- Portability between platforms, sound boards and software is determining factor
- Recommendation: audio/basic, 8-bit ISDN mu-law, 8000 Hz sample rate, mono
*Also* include MPEG audio version of your audio clip for stereo support and CD-quality sound

## Video Clips

- Short video sequences and computer animations
- Portability between platforms and copyright/patent issues are determining factor
- Recommendation: MPEG-1
- When possible, keep MPEG files less than one megabyte for bandwidth and viewer compatibility

## Compound Documents

- Integrated text and graphics in the same document
- Viewer availability, printing, file size, and cost of producing are determining factors
- Recommendation: PostScript Level 1
- In the future, Adobe Acrobat may be the best choice
- Export to HTML when possible to avoid headaches

## Non-traditional Viewers

- You can also serve Word, PowerPoint, Lotus 1-2-3, and other documents
- You must configure the content-type on *both the client and the server*
- application/x-powerpoint	.ppt
- application/x-powerpoint	c:\powerpnt\viewer.exe
- Tell your users about formats and viewers
- Bad example: JPL Planetary Data System images

## Where can I learn more?

- http://sd-www.jsc.nasa.gov/web_formats.html
- Experiment!
- Different recommendations next year
- Webmasters must be flexible (change formats, servers, Content-type, *etc*.) to follow user community (but sometimes you must lead)
- If you disagree with my recommendations, I always enjoy a good argument.