Richard Deeming wrote:

If you've installed an extension

I have installed this extension. Based on your feedback, Ive already uninstalled it. Seems that no harm has been done.

Richard Deeming wrote:

Any extension that claims to be "Chrome dev tools" or similar is almost certainly malicious.

So, you want to say that I installed malicious extension? That may be true. But, how do I know this?

Likewise.

Agree. This vid was cringe at its best. Awful it means.

You have to install extension called Chrome DevTools, activate it, and than code as usual.

You have forgotten the StartPage man........ As an answer to OPs question, this should help. First result especially.