The Chromium Development Documentation Project  / "The Chromium Authors" as per the open source development agreement, CC BY 2.5, via Wikimedia Commons
These days browsers can store a lot of user data on your local computer if you let them. They also urge you to create an account and login so that your browsing data + tons of other data can be synced to a server.
Those who sign-in to Chrome or Chromium with a Google account have no control over what Google does with their data once it leaves their computer. The next best thing is knowing what, where and how the data is being stored/used on a local machine.
There are some interesting ways to view how your own data is being stored by Chromium that I would like to detail below. The first method is looking at internal pages, which can show you quite a bit of what chromium does under the hood. The second method involves looking at user files, which are stored as sqlite databases or json.
One of the great things about Chromium being open source is that anyone can go read the docs, clone and build the source code or follow active development if they wish.
NOTE: There is really only one way to see how things work “under the hood”, but that would require someone skilled and brave enough to go through Chromium’s massive C++ codebase to see how user data actually gets stored and synced in code. I have no shame in admitting that I am not that person, at least not at this point in time.
There are a number of non-listed internal chromium pages that you can see by
typing in the address bar
There’s lots of hyperlinks there that can show a wide variety of information about the state of your browser, system and current user info.
I’ve tried to organize a list of the one’s I found interesting.
|Info about chrome version, OS, extensions, and memory usage.
|Graphics features like OpenGL, Video Decoding and Hardware Acceleration
|Shows input devices relevant to the browser (more useful for ChromeOS)
|Shows every kind of network error possible (at least in the browser)
|Shows every tab with an option to open DevTools for any page or extension
|Provides a debug view for the omnibox and shows extra information like where suggestions come from
|Shows how chrome “predicts” words frequently typed into the omnibox
|Shows your Media Engagement Index on sites.
|A measurement of time spent, scrolls, clicks, typing on a page. More info here
Local Browser State and User Preferences (in json format)
|Some basic browser information
|A large json file with lots of browser state and most if not all user settings
New Tab Data
|The internal url for the new tab page
|A view on data stored for the new tab page
|Suggestions that appear on the new tab page
Generated Events / Actions
|Every event/action that happens in the browser (not page) UI
Signin and Sync
|All information about syncing with a Google Account
|Information about about signed-in Google Accounts
URLS for regular UI pages
Turn on experimental/disabled features
|Turn on/off features with flags – similar to settings command line flags in ~/.config/chromium-flags.conf
Chrome version info
|Detailed/verbose version page
|Less verbose version page
Find your user’s data files on disk
Much of the state of the browser is stored in readable sqlite databases, json files and/or other intermediate types of files (such as those in the cache) that contain binary data.
Files will be in the same directory using Chromium, but likely under the name chromium instead of chrome or google-chrome.
Get a list of sqlite databases used by chromium
$ file ~/.config/chromium/Default/* | grep -i sqlite | cut -d ':' -f 1 | xargs -I@ basename @
Network Action Predictor
Reporting and NEL
These files can all be opened with sqlite3 on the CLI or a SQL GUI such as dbeaver.
Using sqlite to query data
Getting schema and tables from a sqlite db:
sqlite3 <database> '.schema' '.tables' '.exit'
Once you know the table and column where data stored, you can do pretty much anything with it a few examples would be
Export whole url table from History database as a csv
sqlite3 History '.mode csv' 'SELECT * FROM urls' '.exit' > ~/history.csv
Get all origin_urls from logins table in ‘Login Data’ database
sqlite3 'Login Data' 'SELECT origin_url FROM logins' '.exit' > ~/login_urls.txt
Get “keywords” used for search engines stored in ‘Web Data’ database. Output is in json format
sqlite3 'Web Data' '.mode json' 'SELECT * FROM keywords' | jq
There are probably better ways to do this, but I learned a lot from looking at some of these tucked away files. Specifically, I found it interesting that Chrome keeps media and site engagement metrics as well as the preloading/prediction that happens when you start to type in an often visited URL. These are the kind of features you don’t see or think about much as a user, but it’s always there in the background.
I also learned that sqlite can output data in json format. That’s neat.
Compared to digging through the C++ implementation of how all these metrics are created and captured within Chromium, this was both insightful and relatively easy.