duck (@qua3k)

The browser is one of the most used applications in any system. For many, significant portions of their online life flow through their browser and as such, the browser and the developers behind it are in a position to abuse their power to invade peoples' privacy.

As a consequence, projects such as ungoogled-chromium were born to “remove integration with Google services” within the codebase and “enhance privacy, control, and transparency”.

However, there are some glaring flaws with the ungoogled-chromium project. For instance, ungoogled-chromium lags behind upstream Chrome for days every release. The time that n-days are exploitable in ungoogled-chromium is significantly longer than in either Chrome or Edge.

The team also does not ship official binaries and requires users to either trust an additional unknown third party or build from source. It may not be a concern depending on the vendor distributing the binaries, however, and reproducible builds don’t solve this problem.

Keeping that in mind, the third parties that are trusted to distribute prebuilt binaries tend to cripple security features either by weaken exploit mitigations such as Control-Flow Integrity by opting to use system libraries often not compiled with CFI or building with unsupported toolchains.

Furthermore, component updates are disabled, even though components are delivered via the component updater because they require faster out-of-band updates than regular browser updates, and the ungoogled-chromium team does not seem to have any interest in delivering component updates.

Finally, the patches don’t make sense. Performing domain substitution on every URL in the codebase, including documentation and troubleshooting, doesn’t appear to be driven by a real or perceived threat.

In addition, most of the functionality of the patches can be easily driven by disabling crash and metrics reporting in Chrome settings. The patches that can’t be reproduced easily in Chrome settings are in the best case minimally beneficial or actually harmful. Using a browser specifically to gain a perceived notion of privacy should not involve making significant tradeoffs in security.

As such, this blog post is meant to shed some light on the function of ungoogled-chromium patches and how they compare to Chrome’s user facing settings.

Safe Browsing #

The ungoogled-chromium project has written and uses multiple patches to wipe Google’s Safe Browsing service from the codebase even though users can disable Safe Browsing from the settings. For instance:

fix building without safebrowsing #

removes parts of the Safe Browsing service such as the Safe Browsing interstitial.

unrar #

disables “support for safe browsing inspection of rar files”.

disable incident reporting #

disables “the safebrowsing incident reporting where you could upload information about a blocked URL to Google (also added a trk prefix to the URL so we get notified if this happens again in the future).”

disable reporting of safebrowsing override #

disables “reporting of the safebrowsing override, i.e. the report sent if a user decides to visit a page that was flagged as “insecure”. This prevents trk:148 (phishing) and trk:149 (malware)”.

remove unused preferences fields #

removes “unused Safe Browsing and Sign-in fields from the Preferences file”.

Autofill #

The ungoogled-chromium project removes parts of the Autofill service to prevent Chrome from sending “hashed descriptions of the form and its fields” when the user encounters a web form. Note that Autofill can be turned off in Chrome settings.

Default Extensions #

The ungoogled-chromium project disables certain built-in extensions such as the Chrome Web Store, and the exclusive to GOOGLE_CHROME_BRANDING in-app payments support application and Feedback app.

WebResourceService #

ungoogled-chromium removes portions of Chrome’s WebResourceService, used by Chrome’s PluginsResourceService to download security updates to various pepper plugins in Chrome, such as Adobe Flash and the Chrome PDF viewer; this may change with the advent of the Unseasoned PDF viewer and the deprecation of PPAPI.

IPv6 Probes #

ungoogled-chromium uses RIPE NCC servers instead of Google servers for IPv6 probes (connectivity checks) and adds a feature flag for disabling IPv6 probes altogether.

Component Updates #

The ungoogled-chromium project stubs out the URL for component updates, posing a legitimate risk by denying users out-of-band security updates to components such as Chrome’s CRLSets, used to “quickly block certificates in emergency situations”. In contrast, GrapheneOS’s Vanadium subproject disables potentially invasive component updater pings while still allowing for component updates, and they are looking into providing component updates via their own server.

/ new avatar menu #

ungoogled-chromium disables sign-in – it used to additionally control the new avatar menu but doesn’t anymore and never got renamed.


ungoogled-chromium disables the use of RLZ, a promotional tag used to measure searches and Chrome usage. The non-unique tag “contains information about how Chrome was obtained, the week when Chrome was installed, and the week when the first search was performed” and is sent with searches made on Google, telemetry, and crash reports. However, users can “opt-out of sending this data to Google by…installing a version downloaded directly from To opt-out of sending the RLZ string in Chrome OS, press Ctrl + Alt + T to open the crosh shell, type rlz disable followed by the enter key, and then reboot your device.”

Crash Reporting #

ungoogled-chromium disables the uploading of crash reports to Google. However, builds without GOOGLE_CHROME_BRANDING do not report crashes.

Google Domains Functionality #

ungoogled-chromium disables specific features and restrictions applied to Google domains.

Search Engine #

ungoogled-chromium replaces Google with “No Search” (disabling search from omnibox).

Google Accounts (GAIA) #

ungoogled-chromium disables browser management of sign-in of Google Accounts.

Translate #

ungoogled-chromium disables translation and removes the “Translate to” context menu when --translate-script-url is not set.

Domain Substitution #

ungoogled-chromium includes multiple patches to disable all connections hard-coded into the browser using domain substitution. Many of these connections are only made on user interaction and not transparently made in the background.

Connections substituted out include

disable-profile-avatar-downloading.patch #

ungoogled-chromium disables the downloading of high-res profile avatars from Google whenever a user selects an avatar in Chrome settings.

chrome.gcm #

ungoogled-chromium removes the Google Cloud Messaging component of the chrome.gcm API that extensions can use to send messages through Firebase Cloud Messaging.

Domain Reliability #

The Domain Reliability monitor sends info to Google whenever an error occurs while visiting a Google domain. The ungoogled-chromium project disables the creating of the Domain Reliability service in all cases, even though it can be disabled by disabling metrics and crash reporting.

Remote Fonts #

ungoogled-chromium removes references to hardcoded in the browser, replacing them with alternative local fonts.

WebRTC Log Uploader #

ungoogled-chromium disables the uploading of WebRTC logs for the private WebRTC logging APIs used by the Hangouts/Meets services, although it would mean no data would have been uploaded in the first place due to domain substitution.

Local DevTools Files #

ungoogled-chromium always uses local DevTools files instead of remote files from Google.

Browser Network Time #

ungoogled-chromium disables “occasional queries to a Google server to retrieve an accurate timestamp”.

MEI Preloading #

ungoogled-chromium disables downloading of a list of sites with a high Media Engagement Index used to determine whether or not a site autoplays. Users can disable MEI preloading with switch --disable-features=PreloadMediaEngagementData, MediaEngagementBypassAutoplayPolicies

Reporting API #

ungoogled-chromium allows building with enable_reporting = false. (disables Reporting API)

Field Trials #

ungoogled-chromium disables the downloading of field trials (Google’s A/B testing).

Conclusion #

ungoogled-chromium really isn’t a security-oriented browser and is often a regression over Chrome due to various problems with their approach. There are other downstream forks such as Vanadium that add meaningful security improvements that upstream won’t due to performance regressions, but Chrome will always be the first to receive security updates, which is kind of a big thing going for it.

See also #