Not an answer, but if someone came across this question while looking for a Visual Studio Code solution, this worked for me:
{ "version": "0.2.0", "configurations": [ { "type": "chrome", "request": "launch", "name": "Chrome: localhost", "url": "http://localhost:8080", "webRoot": "${workspaceRoot}/app" }, { "type": "chrome", "request": "launch", "runtimeArgs": [ "--incognito" ], "name": "Incog Chrome: localhost", "url": "http://localhost:8080", "webRoot": "${workspaceRoot}/app" } ] }
However, this does not currently work with the Firefox debug extension with the -private-window argument. Hope this helps.
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