And all the browsers need you to sign in if you want multi device sync.
But switching to Chromium does none of that.
Also stripping Google's integration out of Chromium leaves you with a much less capable browser. Are you, for example, willing to use Chromium without Google's Chrome Web Store?
I don't think so. But say that you're willing to keep using Google's Chrome Web Store, Chromium is open source, but the Chrome Web Store is not and all those extensions, reviews and users can't be moved, so what will happen if Google decides to disallow access to its store to Chromium users?
If you think that can't happen, consider that they did it for AOSP Android and that alternatives to Google Play might as well not exist ;-)
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If you're worried about Google's control of Chrome, switching to Chromium does nothing useful, the project is still under Google's control, you're still depending on their good will and you're doing nothing to diminish Chrome's dominance of the market.
What is a priority is building and extending the moat of GApps, locking services into relying on Maps APIs, push notifications, Play Games APIs, etc. Replacing these APIs is a huge task, and many apps will just outright crash if Google Maps isn't on your phone, let alone Google Play Services. The only reprieve is to use F-Droid, which is not the most consistently maintained app store.
Even if Chromium's source is developed by Google employees, it being open source at least allows it to undergo scrutiny with respect to end-user-unfriendly behaviour.
Any proof Chrome does this kind of tracking?
Google interest is not the web, it's its own profit.
This is necessary because the non-profit isn't allowed to do certain things, but a for-profit can, and the non-profit is allowed to own a for-profit.
But I like the analogy because I think people don't consider what online tracking means, and creepy dude on backseat is easy to imagine.
Personally, I have made an effort to try to turn things off in Chrome, because I felt it to be a superior product to FF. I switched to FF purely because I realized that my interests are never going to be aligned with Googles.
The problem is with the rate of change, and lack of UI stability. Can you disable WebRTC? You used to be able to with an easy flag, now its probably harder. Can you disable WebGL? Can't seem to w/o jumping through hoops. Why is Chrome looking at my USB devices? Can I disable WebUSB? nope. Disable Omnibox? Dont think so anymore. You used to be able to IIRC,etc, etc.
Google is never going to make it easy for you to stop sending data to them. An option of "Don't send anything ever, and don't ask me again" would be nice. More and more UXs are employing dark patterns where disabling is never an option, just 'deferring' or 'pausing'. (e.g. https://myaccount.google.com/activitycontrols)
Its hard to make definitive statements because Chrome keeps changing. Now, thats not Chromes fault, of course, but what rate of change is manageable? I don't know.
So, imagine you have two cars to chose from.
The first car, called Chrome, is really cool - it's quick, it's nice, it's reliable, it's comfortable. There's just one thing.
There's a guy on the back seat. He's always there. He writes down wherever you're going. When you go shopping, he makes a copy of the receipt. When you drive with someone, he listens to the conversation and makes notes. Which addresses are you visiting? And how long time do you stay there? And when you make a phone call, he listens and makes notes.
He then keeps this information forever, and sells it to various people and companies. They study you, like a bug, to see what makes you tick. So they know what you like and what you want, and what you're afraid of and where are you in life and so on. So they can manipulate you better into not just buying shit, maybe, but maybe to do more sinister stuff, like manipulate elections.
Of course, the Chrome car makers own some of the important roads, and they make them hard to use in other cars, because they want this dude watching you.
Then there's the Firefox car. It might not be as comfortable or as quick. I think it is, but different people have different experience. But either way, there's no dude making notes. In fact, when there are dudes making notes by the side of the road, the car tries to hide you and protect you!
Or you can use the Safari car, if you get the more expensive garage I guess, whatever.
Why the fuck would anyone use the Chrome car.
EDIT: and the long term Firefox car dfivers say things like "they change how the car looks, might as well go to SpyCar." or "there was some pressure on CEO of FireCar making company for political stuff, might as well switch to SpyCar." And my mind just goes blank?
And the dude on the backseat laughs and laughs as he profiles them so he can manipulate them.