When Mosaic was introduced to the Internet community, it revolutionized net surfing. It's graphical hypertext interface allowed users to seamlessly navigate from location to location on the net, mixing text, graphics, and sound in documents along the way. Mosaic was originally developed by the University of Illinois-Urbana and the National Center for Supercomputer Applications (NCSA), makers of the popular NCSA Telnet for IBM and Macintosh computers. However, Mosaic was only a temporary project. The goal was to develop a complete WWW browser and then allow development to be continued independently. That transition has just occurred. Many of the original programmers who wrote Mosaic now work for Netscape Communications Corporation, and have been developing a similar program called Netscape Navigator. They recently released version 1.0 (after several earlier releases) for free to academic institutions and non-profit users. The replacement of Mosaic by Netscape is inevitable because development of Mosaic has ceased. Netscape also promises to be a superior browser in many ways, primarily in terms of speed. However, these promises should not be accepted blindly. I will compare the features and performance of Mosaic version 2.0 alpha 7 and Netscape Navigator version 1.0 for Windows running under Windows for Workgroups version 3.11 and Microsoft TCP/IP-32. Both of these programs are available for most major graphical environments (Windows, Macintosh, X-Windows) and can be found on The Moment WWW page.
The main advantage Netscape claims over Mosaic is speed. It is true that Netscape includes many features that can reduce transfer times drastically under certain circumstances. Most of the improvements deal with image transfers. For example, if a document has multiple images in it, Netscape can download them simultaneously, whereas Mosaic must download them sequentially. In everyday use, this does often speed things up. Netscape also supports both JPEG and GIF image formats, Mosaic only supports GIFs. JPEG files are generally much smaller than GIF files because of a more sophisticated compression algorithm that they use, and should thus transfer faster than comparable GIF files. In practice, this does not always improve transfer rates. This is because the JPEG files, although smaller, require much more computation to decompress them. On a 486DX2-66, a moderately powerful IBM clone, GIFs and JPEGs tend to transfer at roughly similar speeds. Presumably as processors become more powerful, the smaller JPEG file size will become more advantageous. Another important feature of Netscape is the ability to take action before a transfer is complete. For example, if a web page is loading and you see a link you want to follow, or decide you want to turn around and back up, you do not have to wait for the whole page to be sent. This can be a major time saver.
Netscape also has a slew of tricks to speed up transfers of hypertext documents designed specifically for Netscape Navigator 1.0 or later. One clever trick is multiple resolution graphic images. It is possible to create a hypertext document that will transfer small low resolution images at first, and then after all other text and graphic transfers are completed, go back and replace them with larger high resolution images.
However, for straight data transfers, Mosaic still crushes Netscape on my machine. For example, transferring a 1.7 megabyte sound file from my home page on the CUNIX cluster typically takes 25-35 seconds. Transferring the same file using Netscape 1.0 takes 80-100 seconds. I have been monitoring this particular transfer for several days and at different times of the day, each time doing one Mosaic and one Netscape transfer. This difference can only be due to overhead in the Netscape program itself. Again, this difference should diminish with increasing computational power, but for the time being Mosaic is the clear winner (for the Windows platform at least).
Mosaic and Netscape also require a few important support programs. If you are using Mosaic, and want to be able to view JPEG files externally, a program called LView is included. Although Mosaic can't display JPEG images within hypertext documents, you can configure it to automatically view JPEG files using LView. Netscape does not require this. Most sound clips on the web are available in the AU format. This is supported by Mosaic, but for Netscape an external player is required. For other digitized sound formats, such as WAV, VOC and SND, an external player is required for either program. Although no animation formats are supported by either browser, multimedia files are becoming popular on the net and you may want to get players for them as well. Shareware players for FLI/FLC, AVI, and MPEG animation formats as well as MOV Quicktime movies are widely available.
Netscape has already just about taken over the market for WWW browsers from Mosaic, and completion of this process is guaranteed. However, Mosaic still has a raw speed advantage under certain circumstances, and should not be abandoned yet. I still recommend trying out both programs to see which one suits your browsing needs best. For some, like myself, it may be necessary to keep both programs installed for a while for different purposes.