Spoofing your browser’s user agent

If you are a web developer (or anyone doing any programming which involves web browsers, which is just about everyone nowadays) you really are doing yourself a disservice if you don’t include Firefox in your toolbox for diagnosing issues and testing sites. The community provided Addons for Firefox are just invaluable in day to day tasks. A great example is the ability to spoof your browser’s user agent, pretending to be any browser you want, all from one browser.

My quest to do this started as a curiosity when I found a blog post titled “Search Engine Marketeers are the new script kiddies” discussing a WordPress blog which was hacked in such a way that it invisibly provided more traffic to the hacker’s site whenever a search engine bot crawled the site. The hack was pretty impressive, actually but more impressive was the ability for the blogger to diagnose what had happened and track down the culprit.

Having a few WordPress blogs of my own, I decided to look into checking mine for the same issues. It took me an hour or so of toying and poking around to get everything I needed, so I figured I would take a shot at documenting the steps that went into my adventure in the hopes that someone else would be able to get this done more quickly if they ever needed it. Plus… it will provide a reference for me when I inevitably do this on more computers in the future.

First, you’re going to need to get the User Agent Switcher Addon for Firefox (written by Chris Pederick). Installation should be fairly straight forward, so just click the button while in Firefox and let it do its thing.

Now for the part which took some searching…

The default installation of the Addon doesn’t provide a lot in the way of user agents to switch to. A couple of examples are all that are there, so in order to be really useful you’ll need to add agents of your own or find them somewhere. I found a very complete set of agents conveniently compiled into an XML file which can be imported into the Addon (Options > Options > User Agents > Import) over on Tech Patterns.

Once you have installed the Addon and loaded a complete set of user agents, you can test them out with the QuirksMode Browser Detect page.

There are a lot of uses for this ability, from security to verifying code which reacts to a specific browser. Whatever you use it for, hopefully this short guide made it easier to get your results.