I believe all the current development tools do it wrong, and the right place for a tool is outside the browser, as a custom shell around the main browser compon

I believe all the current development tools do it wrong, and the right place for a tool is outside the browser, as a custom shell around the main browser component. This is how I tend to work: I load up an app. I set up my credentials (by logging in or setting a particular cookie manually, for example). I debug using Firebug, mainly using the DOM view, the console and the JavaScript REPL. Then I might change my credentials to see the page as a different user, for example. I clear the cache now and then, and I clear my cookies often. I also change things like cookie preferences and turn JavaScript on/off to see how my app behaves. I also work on multiple projects concurrently, so I frequently need to switch, meaning yet again to clear the browser state. In other words, I need the browser as a clean slate. I frequently need to throw its state away, and I rarely if ever run pages as "myself". I'm a Chrome user, so for this reason I currently use Firefox as my dedicated debug browser. This means I can always throw away my browser state, and I can close Firefox when I'm done with work. Firefox is a resource hog on OS X, and will frequently sit consuming 5-10% CPU even when idle, so this is actually important. I almost never use Chrome for debugging, not just because its DOM view and console are both much worse than Firebug's, but because it's my browser. (Yes, I know that Chrome supports per-window profiles, but Chrome just isn't good enough for debugging.) My ideal development tool would be a thin shell around a web browser component. It would be chock full of techy dev stuff, and it would not compromise the dev aspect in favour of user-friendliness; unlike today's browsers, everything could be provided natively by the tool instead of inserted awkwardly by "extensions". It would do away with user-facing features like browser extensions, fancy history and bookmarks. In other words, it would be a hard core, bare-bones development tool. This tool would support "projects"; each project being is a browser window, and each browser window is logically compartmentalized, with its own cookie database, history, settings, etc., with the option to save certain things like cookies, so that I can "bake" current browser state and recall it later. The ideal solution would be for each window to be able to embed different browser engines; there is no particular technical reason why this should not work, although it would be a little more work to implement. I actually started writing an app like this for OS X that embeds WebKit. It was surprisingly simple, and I got a decent DOM inspector view and style editor working, but then my mind wandered off to work on something else. I may pick this project up again at some point.