But I think the point is more about how does a regular web app in web land detect devtools? Not, how does an app with DevTools privileges (via a Chrome extensio

But I think the point is more about how does a regular web app in web land detect devtools? Not, how does an app with DevTools privileges (via a Chrome extension, or connecting to the remote debugging port) that controls V8 via debugging APIs detect/prevent if DevTools pane has been opened (there are even APIs/events for this in chrome remote debugging protocol), so no need to rely on the side effects bailout you mention if your goal is to detect DevTools panels and you have "control" over V8. But maybe you're point was more about how would Chrome prevent this DevTools detection? I honestly don't think they would do this, but not because of "overhead"--simply because the console and debugging is useful, and it requires displaying elements, and inspecting those. So there will be no way around having actually printed out elements when DevTools is open. Except if you always printed them out whether it was open or not, but this would be too much overhead, as Chrome only lazily executes console commands (and optimizes things away if DevTools is not open). This is hilarious I'm saying this to you because you work at Lighthouse---so I'm about to learn something I guess! :p ;) xx haha