Yeah. I wanted a test page that could draw attention to things of interest (which specific API is blocked, whether there is obvious randomization going on, etc). FWIW, I edited my earlier message and posted version 1.6. I liked your dark theme too. I expected to see what you reported and I did. I noticed that the AMO page says: "CAUTION! Only version 0.3.0 works with e10s". I also noticed something else. The "Show notifications" option doesn't appear to work when loading my test page from file: or http://test.example/test.html where test.example is hosts file mapped to 127.0.0.1 and a localhost server. The readout is faked but no notification bar. Same result for my normal profile and a fresh portable app version. I do see the notification bar if I use the browser leaks test. Did you see a notification when using my test page (and CanvasBlocker block mode set to fake readout API)? EDIT: For testing purposes I added a ctx.getImageData() call to my code and afterwards CanvasBlocker started to show notifications. So I think notifications may not be triggered by all the calls that can extract canvas data. Exercising all of those wasn't my intention and I'm not sure how best to do it so I'm leaving getImageData() out for now. Also, while looking into that issue I took a look at data URLs. First example is "allow everything", second one is "fake readout API": Looks like the fake readout adds a little noise. At least when canvas.toDataURL() is used to extract data.