Steve Souders has released a new Firefox plugin called “Hammerhead” for measuring web page load times. It has a sweet feature that repeatedly loads pages both with and without the browser cache so you can understand different use cases. One thing Hammerhead will not do for you is slow down your web connection. The page load times that you measure on your development machine will likely be faster than your users' wildest dreams.
Even if you’re not hammering a site, other features make Hammerhead a useful add-on. The Cache & Time panel, shown in Figure 3, shows the current URL’s load time. It also contains buttons to clear the disk and memory cache, or just the memory cache. It has another feature that I haven’t seen anywhere else. You can choose to have Hammerhead clear these caches after every page view. This is a nice feature for me when I’m loading the same page again and again to see it’s performance in an empty or a primed cache state. If you forget to switch this back, it gets reset automatically next time you restart Firefox.
Steve Lamm posted the techniques for working with Hammerhead on the Google Code blog.