Google released their newest gadget for developers yesterday, called "Speed Tracer". It's a plug-in for Chrome's brand-new extension system that purports to show developers exactly where their pages (or web applications, as Google emphasizes) are slowing down. Its run much like any other trace application: open your site in one window and the tracer in another, hit "record", and go about your site performing standard tasks. Speed Tracer will capture data from your site, process it, and display statistics and details for your perusal.
The central feature of Speed Tracer is the "timeline", a graph that shows how "busy" your browser is: presumably 100% would mean that your browser was entirely consumed processing the site, and thus unresponsive to the user. Sections of this timeline are highlighted and displayed in the details pane below, with information on the events causing any slowdowns. You can also view tips or "hintlets" that give advice on how to improve performance.
So much for the tool itself; now, how does it fit into our toolbox? If you're a developer for a standard web site, unfortunately the answer is "not very well". Google is clearly targeting web applications rather than standard web pages with this tool. The main feature of Speed Tracer, the timeline, is somewhat helpful in visualizing the workings of the page, but it's really geared toward ongoing AJAX-like events and performance over multiple pages. For precise page load monitoring, other tools like Firefox's Firebug and the standalone Fiddler utility do a better job of pinpointing event dependencies and bottlenecks. The hintlet system is another disappointment, producing limited and unreliable data (my colleague received no hints at all, and I was only able to pull up a confusing list of hints on one or two of the topics that Google's Page Speed plugin for Firebug already displays).
However, Speed Tracer is not without its uses. For a quick head's up on page performance, the timeline makes a good visual, and if you plan to develop a web application many features could prove useful. For general web developers, though, Speed Tracer will probably be relegated to a subsidiary role next to your main workhorses. This is Google, however, and there's a good chance they'll be adding features and improving the interface, which could turn this tool into a first-class performance tuning device.
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