What exactly does Chrome store in HKEY_CURRENT_USER\Software\Google\Chrome\PreferenceMACs

Question

When I search for topics like moving chrome settings from one machine to another, I often see a references to the registry key HKEY_CURRENT_USER\Software\Google\Chrome\PreferenceMACs. Looking at it, I see directories corresponding to profiles. However, how does it actually work?

The reason I ask is, I use multiple user data directories and multiple profiles within them. The same profile name often shows up under multiple user data directories. So which profile's details actually gets written into the registry?

Let's take the following scenario - I have 2 different chrome browser instances running.

• "C:\Program Files\Google\Chrome\Application\chrome.exe" --user-data-dir="C:\chrome-profiles\work" --profile-directory=hs-main
• "C:\Program Files\Google\Chrome\Application\chrome.exe" --user-data-dir="C:\chrome-profiles\personal" --profile-directory=hs-main

Now, obviously, the registry has a key called hs-main. Is it the work's hs-main or personal's hs-main?

Doing a little bit of testing, it feels like the registry values keep getting overwritten over and over again, depending on which chrome instance was last closed.

So what's the point of the registry entry in the first place? What does it do, how does it affect Chrome's functionality?

EDIT: I am explicitly asking what happens if there are 2 identically named profile directories under different user directories, which is not at all covered in the question that this is marked as a duplicate of, and how to take backup in that case.

(Looks like someone did answer here , so I guess that's the answer, but I would still like to understand how the 2 questions are duplicates of each other)

Answer 1

The PreferenceMACs keys cannot differentiate two profiles with the exact same profile name. Chromium only uses the value from --profile-directory=hs-main, so they are overwriting each other in your case.

Per the source code, the registry keys are used to "track changes to certain preferences, reporting and reacting to them according to preference-specific and browser-wide policies". Different preferences use them for varying purposes, so it's hard to say the total impact. It seems they are mostly used for transactions, to keep track of when a preference was changed in case the save operation got interrupted.

That said, you should consider changing the name of one of your profiles to avoid issues in the future. You can do this without losing data by following the steps here:

Change a name, photo, or color

• On your computer, open Chrome.
• At the top right, click Profile
• Next to "Other Profiles," select Manage profiles
• At the top right of the profile you want to edit, click More More and then Edit.
• Enter a new name or choose a new photo or color theme. Changes are saved automatically.

Then update the --profile-directory in your chrome startup command to match.