The user agent is a digital calling card presented by a web browser when it visits a website, identifying it and telling the website what content is best served to that particular web browser - the simplest example being the web browser on a mobile device will receive content more proportionally formatted for a smaller, portrait screen whereas when viewed from a laptop or desktop, the web browser will deliver the fully featured site.
This user agent can also inform the web site what features it should deploy - an old browser will perhaps be incapable of rendering certain content, so that content can be effectively cut out.
This all becomes relevant, especially to us PowerPC users, when it's possible to present an alternative user agent from the one your web browser natively employs - preferably to lessen CPU load and rendering times.
This has been a feature for a while with standard browser options or add-ons that facilitate selecting different user agents but what I shall discuss in this post is site specific user agents ie user agents that present themselves on a site by site basis automatically as you browse.
This legacy feature is present in the PPC spins of ArcticFox and IceWeasel but wasn't present in TenFourFox (which I'll utilise here) until I asked the developer to reintroduce it which he very generously did.
In the TenFourFox preferences, I leave the user agent at it's default setting and add site specific user agents with TextWrangler editing the TenFourFox prefs.js file that resides in
the last part of that location string may look different on your machine but will always terminate with .default.
This is an example string added to prefs.js:
This process is repeated for all the sites you wish to include - a laborious task admittedly but one you'll only have to do once.
User agents can be copied from online sources or you can even use those included within TenFourFox as standard - select one in preferences, then navigate to whatsmyua and copy/paste the string.
Another method for adding site specific user agents is from within the browser itself - navigate to about:config and right click to add a new string. As per the example above, general.useragent.override.youtube.com is added as the preference name, then NokiaN90-1/3.0545.5.1 Series60/2.8 Profile/MIDP-2.0 Configuration/CLDC-1.1 is added as the string value.
Generally, I will use either the oldest browser I can reasonably get away with or a Nokia mobile user agent for sites where I don't need all the CPU sapping bells and whistles - not only does this show mercy to your ageing PPC Mac but also loads pages quicker and in some cases is refreshingly distraction free.
Some example screens of TenFourFox pretending to be otherwise....