I noticed this tonight but it turned out I was running Firefox and Vivaldi in addition to Chrome. On Windows. So I killed Firefox and used Edge instead. I'm assuming you are running Construct 3 on Windows. But of course you don't have to and you may be on a Mac, Android, or ... Linux.
Assuming Windows, do the three-fingered-salute (Control-Alt-Delete) and see what else is running with Task Manager. I saw that Firefox was hogging way too much memory. Construct 3
I killed Chrome and Vivaldi, and then restarted Chrome. There was one instance of Chrome at 100MB, and when I started Construct 3, that added another 100MB, and when I ran a small game from Construct 3, that added a third instance at 100MB (your MB may vary). But that's still less than Firefox, which was chugging along at 400MB+.
So if you are making a report, let us know the following:
Operating System (me: Windows 10 Enterprise 64-bit
Browser: Chrome 58.0
Construct 3: r39
Switching to Chrome Canary sometimes gives you improvement, sometimes not. The bottom line to see what else is running on your machine, make sure your machine is good enough, and that everything is up to date.
Is anyone keeping a list of what Construct 3 runs on? Chrome we know. But it also runs on Vivaldi, Brave, and Opera (fans of Chrome), but doesn't seem happy on Firefox or Microsoft Edge.