Designing websites for low bandwidth
The lowest common denominator is the first issue a web designer needs to address. The type of connection and the type of computer used to access a websit will dictate if a website can load at all. Such forethought is especially necessary for websites that target users in developing nations, such as Africa. Few people want to wait for a minute or more for a high resolution image (that may not even be completely relevant to the article) to load. In that same minute, a user could read multiple paragraphs of useful text. oAfrica.com, for example, takes 9.1 seconds to load over a fast connection, with images composing 60% of the 486kb. Not a good sign. In fact, this site would take nearly 6 minutes to load over a 14.4 modem, under ideal conditions. Fortunately, the Onlina Africa mobile page is only 29kb, close to the ideal 25kb size based on average bandwidth speeds at African universities.
In the United States, media-intensive sites rely on uncongested broadband connections that can transfer at 256kbps or more and have much less latency than satellite transfers. However, most Africans rely on either:
- congested broadband connections whose speed is far from ideal
- satellite connections where the transfer latency is around 250ms
Some users, particularly in South Africa or along the coasts where undersea cables terminate, do have moderately fast connections and can enjoy more advanced web design. However, adequate connection speeds can be spotty, and vary with time of day, so quality is by no means guaranteed over a private line or internet café. Even universities with 1.2Mbps connections have greatly reduced bandwidth per computer if only 5% of the network is accessing the Internet. Finally, greater numbers of users are accessing websites via low-res mobile devices connected to sub-3G networks.
However, this doesn’t mean that a site needs to be written in text-only HTML (View oAfrica.com in text format). Fortunately, there are multiple sources that explain web design guidelines for low bandwidth, most notably, a page at aptivate.org. Some suggestions:
- Don’t create pages greater than 25kb. The goal is to have a 10-15 second load time at 20kbps – a very tough task. If useful data appears within 2 seconds, visitors will wait up to 30 seconds.
- Use CSS to reduce images and maintain a clean site structure. Don’t require more than a couple of clicks.
- Allow pages to be cached. This will reduce the load time for frequent visitors.
- Avoid PDFs and scripting. If links to large files are necessary, show the file size.
- Content is king: put useful information first.
Additionally, Africa is a nation whose culture is heavily rooted in oral communication. Video is a great tool, and is certainly more entertaining than words, but perhaps is not as useful to the typical African internet user. If rich media is to be used, the Science Media Network provides some insight:
- Provide MP3 at 32kbps, and provide a text-alternative, when possible. Never auto-load a media file.
- Try to encode video in Flash+H.264. Never use uncompressed video.
In the meantime, Africans with slow internet connections must realize that they are at a disadvantage to much of the world. Thus far, it seems as if African internet users have great patience. According to Alexa, YouTube is typically one of the ten most popular sites in every African country.
Update (10/20/09): John Liebhardt at Global Voices Online has written an excellent post on this very subject. He stresses the importance of low-band design in order to serve the mobile audience.