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<h1 id="faq">
<a href="#faq">Frequently Asked Questions</a>
</h1>
<p>This page contains answers to frequently asked questions about GrapheneOS. It's not
an overview of the project or a list of interesting topics about GrapheneOS. Many of
the answers would be nearly the same or identical for the latest release of the
Android Open Source Project. The goal is to provide high quality answers to some of
the most common questions about the project, so the developers and other community
members can link to these and save lots of time while also providing higher quality
answers.</p>
<h2 id="table-of-contents">
<a href="#table-of-contents">Table of contents</a>
</h2>
<ul>
<li>
<a href="#device-support">Device support</a>
<ul>
<li><a href="#supported-devices">Which devices are supported?</a></li>
<li><a href="#recommended-devices">Which devices are recommended?</a></li>
<li><a href="#future-devices">Which devices will be supported in the future?</a></li>
<li><a href="#when-devices">When will more devices be supported?</a></li>
<li><a href="#legacy-devices">Why are older devices no longer supported?</a></li>
</ul>
</li>
<li>
<a href="#security-and-privacy">Security and privacy</a>
<ul>
<li><a href="#clipboard">Can apps spy on the clipboard in the background
or inject content into it?</a></li>
<li><a href="#hardware-identifiers">Can apps access hardware
identifiers?</a></li>
<li><a href="#non-hardware-identifiers">What about non-hardware identifiers?</a></li>
<li><a href="#cellular-tracking">What does GrapheneOS do about cellular
tracking and silent SMS?</a></li>
<li><a href="#default-connections">Which connections do the OS and
bundled apps make by default?</a></li>
<li><a href="#default-dns">Which DNS servers are used by default?</a></li>
<li><a href="#custom-dns">How do I use a custom DNS server?</a></li>
<li><a href="#private-dns-ip">Why does Private DNS not accept IP
addresses?</a></li>
<li><a href="#private-dns-other">Does DNS-over-TLS (Private DNS) protect
other connections?</a></li>
<li><a href="#private-dns-visited">Does DNS-over-TLS (Private DNS) hide
which sites are visited, etc.?</a></li>
<li><a href="#vpn-support">What kind of VPN and Tor support is available?</a></li>
<li><a href="#network-monitoring">Can apps monitor network connections or
statistics?</a></li>
<li><a href="#firewall">Does GrapheneOS provide a firewall?</a></li>
<li><a href="#ad-blocking">How can I set up system-wide ad-blocking?</a></li>
<li><a href="#ad-blocking-apps">Are ad-blocking apps supported?</a></li>
<li><a href="#baseband-isolation">Is the baseband isolated?</a></li>
</ul>
</li>
<li>
<a href="#day-to-day-use">Day to day use</a>
<ul>
<li><a href="#updates">How do I keep the OS updated?</a></li>
<li><a href="#updates-sideloading">How do I update without connecting the
device to the internet?</a></li>
</ul>
</li>
<li><a href="#anti-theft">Does GrapheneOS provide Factory Reset Protection?</a></li>
<li><a href="#bundled-apps">Why aren't my favorite apps bundled with GrapheneOS?</a></li>
</ul>
<h2 id="device-support">
<a href="#device-support">Device support</a>
</h2>
<h3 id="supported-devices">
<a href="#supported-devices">Which devices are supported?</a>
</h3>
<p>GrapheneOS has official production support for the Pixel 2 (legacy), Pixel 2 XL
(legacy), Pixel 3, Pixel 3 XL, Pixel 3a, Pixel 3a XL, Pixel 4 and Pixel 4 XL. Pixel 4a
support is experimental. The release tags for these devices have official builds and
updates available. These devices meet the stringent privacy and security standards and
have substantial upstream and downstream hardening specific to the devices.</p>
<p>Many other devices are supported by GrapheneOS at a source level, and it can be
built for them without modifications to the existing GrapheneOS source tree. Device
support repositories for the Android Open Source Project can simply be dropped into
the source tree, with at most minor modifications within them to support GrapheneOS.
In most cases, substantial work beyond that will be needed to bring the support up to
the same standards. For most devices, the hardware and firmware will prevent providing
a reasonably secure device, regardless of the work put into device support.</p>
<p>GrapheneOS also supports generic targets, but these aren't suitable for production
usage and are only intended for development and testing use. For mobile devices, the
generic targets simply run on top of the underlying device support code (firmware,
kernel, device trees, vendor code) rather than shipping it and keeping it updated. It
would be possible to ship generic system images with separate updates for the device
support code. However, it would be drastically more complicated to maintain and
support due to combinations of different versions and it would cause complications for
the hardening done by GrapheneOS. The motivation doesn't exist for GrapheneOS, since
full updates with deltas to minimize bandwidth can be shipped for every device and
GrapheneOS is the only party involved in providing the updates. For the same reason,
it has little use for the ability to provide out-of-band updates to system image
components including all the apps and many other components.</p>
<p>Some of the GrapheneOS sub-projects support other operating systems on a broader
range of devices. Device support for Auditor and AttestationServer is documented in
the <a href="https://attestation.app/about">overview of those projects</a>. The
<a href="https://github.com/GrapheneOS">hardened_malloc</a> project supports nearly
any Linux-based environment due to official support for musl, glibc and Bionic along
with easily added support for other environments. It can easily run on non-Linux-based
operating systems too, and supporting some like HardenedBSD is planned but depends on
contributors from those communities.</p>
<h3 id="recommended-devices">
<a href="#recommended-devices">Which devices are recommended?</a>
</h3>
<p>The recommended devices with the best hardware, firmware and software security
along with the longest future support time are the Pixel 4, 4 XL and 4a. Pixel 4a
support is still experimental and it isn't supported by Auditor yet.</p>
<p>On the Pixel 4 and 4 XL, support for fingerprint unlock as a secondary unlock
mechanism has been removed and replaced with IR-based 3D facial scanning. GrapheneOS
plans to extend secondary unlock support with the option of 2-factor authentication
using a secondary PIN or passphrase required for fingerprint / face unlock. The Pixel
4a has a fingerprint scanner instead of the dual infrared face scanning cameras.</p>
<p>The Pixel 3a and 3a XL are budget devices meeting the same security standards as
the more expensive flagship devices. Compared to the Pixel 3a and 3a XL, the flagship
Pixel 3 and Pixel 3 XL have wireless charging, dual front-facing speakers, the Pixel
Visual Core supporting HDR+ with compatible apps on GrapheneOS, IP68 dust and water
protection, a higher-end screen, slightly more durable glass and of course a stronger
CPU, GPU, cellular radio, etc. You should get one of the budget devices if these
things aren't compelling to you. The Pixel 3a and 3a XL do have one extra feature: an
analog headphone port as an alternative to wireless audio and digital USB-C audio.</p>
<h3 id="future-devices">
<a href="#future-devices">Which devices will be supported in the future?</a>
</h3>
<p>Devices are carefully chosen based on their merits rather than the project aiming
to have broad device support. Broad device support is counter to the aims of the
project, and the project will eventually be engaging in hardware and firmware level
improvements rather than only offering suggestions and bug reports upstream for those
areas. Much of the work on the project involves changes that are specific to different
devices, and officially supported devices are the ones targeted by most of this
ongoing work.</p>
<p>Devices need to be meeting the standards of the project in order to be considered as
potential targets. In addition to support for installing other operating systems,
standard hardware-based security features like the hardware-backed keystores, verified
boot, attestation and various hardware-based exploit mitigations need to be available.
Devices also need to have decent integration of IOMMUs for isolating components such
as the GPU, radios (NFC, Wi-Fi, Bluetooth, Cellular), media decode / encode, image
processor, etc., because if the hardware / firmware support is missing or broken,
there's not much that the OS can do to provide an alternative. Devices with support for
alternative operating systems as an afterthought will not be considered. Devices need
to have proper ongoing support for their firmware and software specific to the hardware
like drivers in order to provide proper full security updates too. Devices that are
end-of-life and no longer receiving these updates will not be supported.</p>
<p>In order to support a device, the appropriate resources also need to be available
and dedicated towards it. Releases for each supported device need to be robust and
stable, with all standard functionality working properly and testing for each of the
releases.</p>
<p>Hardware, firmware and software specific to devices like drivers play a huge role
in the overall security of a device. The goal of the project is not to slightly
improve some aspects of insecure devices and supporting a broad set of devices would
be directly counter to the values of the project. A lot of the low-level work also
ends up being fairly tied to the hardware.</p>
<h3 id="when-devices">
<a href="#when-devices">When will more devices be supported?</a>
</h3>
<p>Broader device support can only happen after the community (companies,
organizations and individuals) steps up to make substantial, ongoing contributions to
making the existing device support sustainable. Once the existing device support is
more sustainable, early research and development work for other devices can begin.
Once a device is deemed to be a worthwhile target, the project needs maintainers to
develop and maintain support for it including addressing device-specific issues that
are uncovered, which will include issues uncovered in the device support code by
GrapheneOS hardening features.</p>
<p>It's not really a matter of time but rather a need for community support for the
project increasing. As an open source project, the way to get something to happen in
GrapheneOS is to contribute to it, and this is particularly true for device support
since it's very self-contained and can be delegated to separate teams for each
device. If you want to see more devices supported sooner, you should get to work on
identifying good devices with full support for alternative operating systems with
verified boot, etc. and then start working on integrating and testing support.</p>
<p>It should also be clear that the expectation is for people to buy a device to run
GrapheneOS, rather than GrapheneOS supporting their existing devices. This will only
become more true if GrapheneOS is successful enough to accomplish the goal of having
devices produced based on an SoC reference design with minor improvements for privacy
and security. Broad device support is the opposite of what the project wants to
achieve in the long term.</p>
<h3 id="legacy-devices">
<a href="#legacy-devices">Why are older devices no longer supported?</a>
</h3>
<p>GrapheneOS aims to provide reasonably private and secure devices. It cannot do that
once device support code like firmware, kernel and vendor code is no longer actively
maintained. Even if the community was prepared to take over maintenance of the open
source code and to replace the rest, firmware would present a major issue, and the
community has never been active or interested enough in device support to consider
attempting this. Unlike many other platforms, GrapheneOS has a much higher minimum
standard than simply having devices fully functional, as they also need to provide the
expected level of security. It would start to become realistic to provide
substantially longer device support once GrapheneOS controls the hardware and firmware
via custom hardware manufactured for it. Until then, the lifetime of devices will
remain based on manufacturer support. It's also important to keep in mind that phone
vendors claiming to provide longer support often aren't actually doing it and some
never even ship firmware updates when the hardware is still supported by the
vendors...</p>
<p>GrapheneOS also has high standards for the privacy and security properties of the
hardware and firmware, and these standards are regularly advancing. The rapid pace of
improvement has been slowing down, but each hardware generation still brings major
improvements. Over time, the older hardware starts to become a substantial liability
and holds back the project. It becomes complex to simply make statements about the
security of the project when exceptions for old devices need to be listed out. The
project ends up wanting to drop devices for this reason but has always kept them going
until the end-of-life date to provide more time for people to migrate.</p>
<h2 id="security-and-privacy">
<a href="#security-and-privacy">Security and privacy</a>
</h2>
<h3 id="clipboard">
<a href="#clipboard">Can apps spy on the clipboard in the background or inject
content into it?</a>
</h3>
<p>As of Android 10, only the configured default input method editor (your keyboard of
choice) and the currently focused app can access the clipboard. Apps without focus
cannot access the clipboard. This is a stricter restriction than preventing apps in
the background from accessing it, since an app in the foreground or a foreground
service cannot access it, only the foreground app that's currently focused. Clipboard
managers need to be implemented by the keyboard chosen as the default by the user.</p>
<p>GrapheneOS previously restricted background clipboard access as a much earlier and
slightly less strict implementation of this feature. It provided a toggle for users to
whitelist clipboard managers, which is no longer needed now that keyboards are
expected to provide it.</p>
<h3 id="hardware-identifiers">
<a href="#hardware-identifiers">Can apps access hardware identifiers?</a>
</h3>
<p>As of Android 10, apps cannot obtain permission to access non-resettable hardware
identifiers such as the serial number, MAC addresses, IMEIs/MEIDs, SIM card serial
numbers and subscriber IDs. Only privileged apps included in the base system with
<code>READ_PRIVILEGED_PHONE_STATE</code> whitelisted can access these hardware
identifiers. Apps targeting Android 10 will receive a <code>SecurityException</code>
and older apps will receive an empty value for compatibility.</p>
<p>Since these restrictions became standard, GrapheneOS only makes a small change to
remove a legacy form of access to the serial number by legacy apps, which was still
around for compatibility. It used to need more extensive changes such as disallowing
access to the serial number but those restrictions are now standard.</p>
<p>Apps can determine the model of the device (such as it being a Pixel 4) either
directly or indirectly through the properties of the hardware and software. There
isn't a way to avoid this short of the OS supporting running apps in a virtual machine
with limited functionality and hardware acceleration. Hiding the CPU/SoC model would
require not even using basic hardware virtualization support and these things could
probably still be detected via performance measurements.</p>
<h3 id="non-hardware-identifiers">
<a href="#non-hardware-identifiers">What about non-hardware identifiers?</a>
</h3>
<p>In addition to not having a way to identify the hardware, apps cannot directly
identify the installation of the OS on the hardware. Apps only have a small portion of
the OS configuration exposed to them and there is not much for device owners to change
which could identify their installation. Apps can detect that they're being run on
GrapheneOS via the privacy and security features placing further restrictions on them
and hardening them against further exploitation. Apps can identify their own app
installation via their app data and can directly (until that's removed) or indirectly
identify a profile. Profiles should be used when separate identities are desired.
Profiles can be used as temporary ephemeral identifies by creating them for a specific
need and then deleting them. The rest of this answer only provides more technical
details, so you can stop reading here if you only want an overview and actionable
advice (i.e. use profiles as identities not inherently tied to each other).</p>
<p>Apps can generate their own 128-bit or larger random value and use that as an
identifier for the app installation. Apps can create data in their app-specific
external storage directory by default without needing permission, and in the legacy
storage model before API 29 that data persists after the app is uninstalled, so it can
be used to store an ID that persists through the app being uninstalled and
reinstalled. However, external storage is under control of the user and the user can
delete this data at any time, including after uninstalling the app. In the modern
storage model, this data is automatically removed when the app is uninstalled.
GrapheneOS includes Seedvault as an OS backup service which must be explicitly
enabled, and it has the option to automatically restore app data when an app is
reinstalled, so it wouldn't lose track of it being the same profile.</p>
<p>The <code>ANDROID_ID</code> string is a 64-bit random number, unique to each
combination of profile and app signing key. The 64-bit limitation means it isn't
particularly useful due to the possibility of collisions. It's tied to the lifetime of
profiles and does not persist through profile deletion or a factory reset. This is
comparable to an app targeting the legacy storage model storing a 64-bit random value
in the app-specific external storage directory. In the future, GrapheneOS will likely
change this to be tied to the lifetime of app installations rather than profiles. An
app could still track the identity of the profile through data you give it access to or
via data another app chooses to share with them.</p>
<p>The advertising ID is a Google Play services feature not included in the baseline
Android API, so it isn't an API included in GrapheneOS. The advertising ID is unique
to each profile. It isn't unique to each app signing key like <code>ANDROID_ID</code>,
but that makes little difference since apps within the same profile can communicate
with each other with mutual consent. It's comparable to <code>ANDROID_ID</code> but
provides an 128-bit value so it provides a strong cryptographic guarantee against
collisions, although a device messing with apps could set it to the same value used in
another profile. The advertising ID is exposed via the Settings app and can be reset
to a new random value, unlike <code>ANDROID_ID</code> which remains the same for the
lifetime of the profile, but apps can tie it the previous ID since they can detect
that it changed via their own ID in their app data.</p>
<p>Apps do not have access to user data by default and cannot ever access the data of
other apps without those apps going out of the way to share it with them. If apps are
granted read access to user data like media or contacts, they could use it to identify
the profile. If apps are granted write access to user data, they could tag it to keep
track of the profile. Apps previously had little reason to do things like this because
they were able to persist data through an uninstall and reinstallation by default. The
modern storage model means they need to request access to user data to do this. The
existence of <code>ANDROID_ID</code> means they don't yet need to bother with that but
that will change on GrapheneOS and will likely change for baseline Android too.
However, profiles are the only way to provide a strong assurance of separate
identities since the application model of the OS is designed to support communication
between apps within the same profile, but never between them.</p>
<h3 id="cellular-tracking">
<a href="#cellular-tracking">What does GrapheneOS do about cellular tracking and
silent SMS?</a>
</h3>
<p>GrapheneOS always considers the network to be hostile and does not implement weak
or useless mitigations. Therefore, it does not have the assorted gimmicks seen elsewhere
providing privacy/security theatre to make users feel better about these issues. One
of the core tenets of GrapheneOS is being honest with users and avoiding scams/frills
based around marketing rather than real world privacy/security threat models.</p>
<p>Activating airplane mode will fully disable the cellular radio transmit and receive
capabilities, which will prevent your phone from being reached from the cellular
network and stop your carrier (and anyone impersonating them to you) from tracking the
device via the cellular radio. The baseband implements other functionality such as
Wi-Fi and GPS functionality, but each of these components is separately sandboxed on
the baseband and independent of each other. Enabling airplane mode disables the
cellular radio, but Wi-Fi can be re-enabled and used without activating the cellular
radio again. This allows using the device as a Wi-Fi only device.</p>
<p>Even if interception of the connection or some other man-in-the-middle attack along
the network is not currently occurring, the network is still untrustworthy and
information should not be sent unencrypted. Legacy calls and texts should be avoided
as they're not secure and trust the carrier / network along with having weak security
against other parties. Trying to detect some forms of interception rather than dealing
with the root of the problem (unencrypted communications / data transfer) would be
foolish and doomed to failure.</p>
<p>Receiving a silent SMS is not a good indicator of being targeted by your cell
carrier, police or government because <em>anyone on the cell network can send
them</em> including yourself. Cellular triangulation will happen regardless of whether
or not SMS texts are being sent or received by the phone. Even if an SMS did serve a
useful purpose for tracking, a silent SMS would be little different than receiving
unsolicited spam. In fact, sending spam would be stealthier since it wouldn't trigger
alerts for silent SMS but rather would be ignored with the rest of the spam. Regardless,
sending texts or other data is not required or particularly useful to track devices
connected to a network for an adversary with the appropriate access.</p>
<h3 id="default-connections">
<a href="#default-connections">What kind of connections do the OS and bundled apps
make by default?</a>
</h3>
<p>GrapheneOS makes connections to the outside world to test connectivity, detect
captive portals and download updates. No data varying per user / installation / device
is sent in these connections. There aren't analytics / telemetry in GrapheneOS.</p>
<p>The expected default connections by GrapheneOS (including all base system apps) are
the following:</p>
<ul>
<li>
<p>The GrapheneOS Updater app fetches update metadata from
https://releases.grapheneos.org/DEVICE-CHANNEL approximately once every four hours
when connected to a permitted network for updates.</p>
<p>Once an update is available, it tries to download
https://releases.grapheneos.org/DEVICE-incremental-OLD_VERSION-NEW_VERSION.zip
for a delta update, and then falls back to
https://releases.grapheneos.org/DEVICE-ota_update-NEW_VERSION.zip.</p>
<p>No query / data is sent to the server, so the only information leaked to it
are the variables in these 3 URLs (device, channel, current version) which is
necessary to obtain the update.</p>
<p>Users are in control of which types of networks the Updater app will use
and can disable the Updater app in extreme cases. It's strongly recommended to
leave it enabled to quickly receive security updates including updates outside
the regular monthly schedule.</p>
<p>The update client avoids trusting the data obtained from the update server
via signature verification with downgrade protection. Verified boot provides
another layer of signature verification with downgrade protection. GrapheneOS
servers do not have access to GrapheneOS signing keys.</p>
<p>See the <a href="/usage#updates">usage guide's section on updates</a> for
more information.</p>
</li>
<li>
<p>An HTTPS connection is made to https://time.grapheneos.org/ to update the
time from the date header field. This is a full replacement of Android's
standard network time update implementation, which uses the cellular network
when available with a fallback to SNTP when it's not available. Network time
updates are security sensitive since certificate validation depends on having
an accurate time, but the standard NTP / SNTP protocols used across most OSes
have no authentication.</p>
<p>We plan to offer a toggle to use the standard functionality instead of
HTTPS-based time updates in order to blend in with other devices.</p>
<p>Network time can be disabled with the toggle at Settings ➔ System ➔ Date
& time ➔ Use network-provided time. Unlike AOSP or the stock OS on the
supported devices, GrapheneOS stops making network time connections when using
network time is disabled rather than just not setting the clock based on it.
The time zone is still obtained directly via the time zone provided by the
mobile network when available.</p>
</li>
<li>
<p>On devices with a Qualcomm baseband (which provides GPS), when location
functionality is enabled and being used,
<a href="https://en.wikipedia.org/wiki/GPS_signals#Almanac">GPS almanacs</a>
are downloaded from https://xtrapath1.izatcloud.net/xtra3grc.bin,
https://xtrapath2.izatcloud.net/xtra3grc.bin or
https://xtrapath3.izatcloud.net/xtra3grc.bin which are currently (as of
September 2020) hosted via Amazon Web Services. GrapheneOS has modified all
references to these servers to use HTTPS rather than a mix of HTTP and HTTPS.
No query / data is sent to the server.</p>
<p>We plan to offer the option to download these files from the GrapheneOS
servers, but we'll retain the option to use the standard servers to blend in
with other devices.</p>
</li>
<li>
<p>Connectivity checks designed to mimic a web browser user agent are performed
by using HTTP and HTTPS to fetch standard URLs generating an HTTP 204 status
code. This is used to detect when internet connectivity is lost on a network,
which triggers fallback to other available networks if possible. These checks
are designed to detect and handle captive portals which substitute the
expected empty 204 response with their own web page.</p>
<p>By default, GrapheneOS leaves these set to the standard four URLs to blend
into the crowd of billions of other Android devices with and without Google
Mobile Services performing the same empty GET requests. For privacy reasons,
it isn't desirable to stand out from the crowd and changing these URLs or even
disabling the feature will likely reduce your privacy by giving your device a
more unique fingerprint. GrapheneOS aims to appear like any other common
mobile device on the network.</p>
<p>These need use a very common domain and URL in order to bypass whitelisting
systems only permitting access to common domains / URLs so you may experience
issues if you choose to use connectivitycheck.grapheneos.org instead of the
standard URLs.</p>
<p>Standard frozen AOSP user agent for the GET request:</p>
<p>Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.32 Safari/537.36</p>
<p>No query / data is sent to the servers and the response is unused beyond
checking the response code.</p>
<p>Standard URLs used by Android and when blending in with other devices on
GrapheneOS:</p>
<ul>
<li>HTTPS: https://www.google.com/generate_204</li>
<li>HTTP: http://connectivitycheck.gstatic.com/generate_204</li>
<li>HTTP fallback: http://www.google.com/gen_204</li>
<li>HTTP other fallback: http://play.googleapis.com/generate_204</li>
</ul>
<p>We have our own connectivitycheck.grapheneos.org server as an alternative
to using the standard URLs. This can currently be enabled by users interested
in using it via the developer tools. Providing a toggle in the Settings app
for using connectivitycheck.grapheneos.org as an alternative
<a href="https://github.com/GrapheneOS/os_issue_tracker/issues/198">is
planned</a>. The option to blend into the crowd with the standard URLs is
important and must remain supported for people who need to be able to blend in
rather than getting the nice feeling that comes from using GrapheneOS
servers.</p>
<ul>
<li>HTTPS: https://connectivitycheck.grapheneos.org/generate_204</li>
<li>HTTP: http://connectivitycheck.grapheneos.org/generate_204</li>
</ul>
<p>We do not currently provide a separate fallback domain so the fallback HTTP
fallback should be set to
http://connectivitycheck.grapheneos.org/generate_204.</p>
<p>Similar connectivity checks are also performed by Vanadium. Configuration
will need to be extended to these, likely by reusing the OS configuration
instead of it being separate.</p>
</li>
<li>
<p>DNS connectivity and functionality tests</p>
</li>
<li>
<p>DNS resolution for other connections</p>
</li>
</ul>
<h3 id="default-dns">
<a href="#default-dns">Which DNS servers are used by default?</a>
</h3>
<p>By default, the OS uses the network-provided DNS servers, whether those come from
DHCP or static network configuration. If no DNS servers are provided, GrapheneOS uses
<a href="https://developers.cloudflare.com/1.1.1.1/what-is-1.1.1.1/">Cloudflare DNS</a>
as the fallback rather than Google Public DNS. In practice, the fallback is rarely
used and has little real world impact.</p>
<h3 id="custom-dns">
<a href="#custom-dns">How do I use a custom DNS server?</a>
</h3>
<p>It isn't possible to directly override the DNS servers provided by the network via
DHCP. Instead, use the Private DNS feature in Settings ➔ Network & internet ➔
Advanced ➔ Private DNS to set the hostname of a DNS-over-TLS server. It needs to have
a valid certificate such as a free certificate from Let's Encrypt. The OS will look up
the Private DNS hostname via the network provided DNS servers and will then force all
other DNS requests through the Private DNS server. Unlike an option to override the
network-provided DNS servers, this prevents the network from monitoring or tampering
with DNS requests/responses.</p>
<p>As an example, set the hostname to <code>one.one.one.one</code> for Cloudflare DNS.
There are various other mainstream DNS-over-TLS options available including Quad9,
Google and AdGuard.</p>
<p>Configuring a static IP address for a network requires entering DNS servers
manually, but you should still use the Private DNS feature with it, and you shouldn't
misuse the static IP address option just to override the DNS servers.</p>
<p>VPN service apps can also provide their own DNS implementation and/or servers,
including an alternate implementation of encrypted DNS. Private DNS takes precedence
over VPN-provided DNS, since it's just the network-provided DNS.</p>
<p>Apps and web sites can detect the configured DNS servers by generating random
subdomains resolved by querying their authoritative DNS server. This can be used as
part of fingerprinting users. If you're using a VPN, you should consider using the
standard DNS service provided by the VPN service to avoid standing out from other
users.</p>
<h3 id="private-dns-ip">
<a href="#private-dns-ip">Why does Private DNS not accept IP addresses?</a>
</h3>
<p>By default, in the automatic mode, the Private DNS feature provides opportunistic
encryption by using DNS-over-TLS when supported by the DNS server IP addresses
provided by the network (DHCP) or the static IP configuration. Opportunistic
encryption provides protection against a passive listener, not an active attacker,
since they can force falling back to unencrypted DNS by blocking DNS-over-TLS. In the
automatic mode, certificate validation is not enforced, as it would provide no
additional security and would reduce the availability of opportunistic encryption.</p>
<p>When Private DNS is explicitly enabled, it uses authenticated encryption without a
fallback. The authentication is performed based on the hostname of the server, so it
isn't possible to provide an IP address. The OS will look up the hostname of the Private
DNS server via unencrypted DNS and then force all other DNS lookups via DNS-over-TLS
with the identity of the server authenticated as part of providing authenticated
encryption.</p>
<h3 id="private-dns-other">
<a href="#private-dns-other">Does DNS-over-TLS (Private DNS) protect other connections?</a>
</h3>
<p>No, it only provides privacy for DNS resolution. Even authenticating DNS results
with DNSSEC does not protect other connections, unless the DNS records are part of the
system used to provide authenticated encryption, and DNS-over-TLS is not a substitute
for DNSSEC. If connections have authenticated encryption, they're secure even if DNS
resolution is hijacked by an attacker. If connections do not have authenticated
encryption, an attacker can listen in and tamper with them without hijacking DNS.
There are other ways to perform a MITM attack than DNS hijacking and internet routing
is fundamentally insecure. DNS-over-TLS may make a MITM harder for some attackers, but
don't count on it at all.</p>
<h3 id="private-dns-visited">
<a href="#private-dns-visited">Does DNS-over-TLS (Private DNS) hide which sites are visited, etc.?</a>
</h3>
<p>Private DNS only encrypts DNS, and an adversary monitoring connections can still
see the IP address at the other end of those connections. Many domains resolve to
ambiguous IP addresses, so encrypted DNS is part of what's required to take away a lot
of the information leaked to adversaries. However, TLS currently leaks domains via
SNI, so encrypted DNS is not yet accomplishing much. It's a forward looking feature
that will become more useful in the future. Using it is recommended, but it's not an
alternative to using Tor or a VPN.</p>
<h3 id="vpn-support">
<a href="#vpn-support">What kind of VPN and Tor support is available?</a>
</h3>
<p>VPNs can be configured under Settings ➔ Network & Internet ➔ Advanced ➔ VPN.
Support for the following protocols is included: PPTP (insecure, obsolete), L2TP/IPSec
PSK, L2TP/IPSec RSA, IPSec Xauth PSK, IPSec Xauth RSA and IPSec Hybrid RSA. Apps can
also provide userspace VPN implementations and the following open source apps are
recommended: Orbot (Tor), WireGuard, OpenVPN for Android and the Private Internet
Access client (OpenVPN).</p>
<p>VPN configurations created with the built-in support can be set as the always-on
VPN in the configuration panel. This will keep the VPN running, reconnecting as
necessary and will force all connections through them. An app providing a VPN service
can also be set as the always-on VPN via the entry in the Settings page. For app-based
VPN implementations, there's also an additional "Block connections without VPN" toggle
which is needed to prevent leaks when the app's VPN service isn't running.</p>
<h3 id="network-monitoring">
<a href="#network-monitoring">Can apps monitor network connections or statistics?</a>
</h3>
<p>Apps cannot monitor network connections unless they're made into the active VPN
service by the user. Apps cannot normally access network stats and cannot directly
request access to them. However, app-based stats can be explicitly granted by users as
part of access to app usage stats in Settings ➔ Apps & notifications ➔ Special app
access ➔ Usage access.</p>
<p>This was previously part of the GrapheneOS privacy improvements, but became a
standard Android feature with Android 10.</p>
<h3 id="firewall">
<a href="#firewall">Does GrapheneOS provide a firewall?</a>
</h3>
<p>Yes, GrapheneOS inherits the deeply integrated firewall from the Android Open
Source Project, which is used to implement portions of the security model and various
other features. The GrapheneOS project historically made various improvements to the
firewall but over time most of these changes have been integrated upstream or became
irrelevant.</p>
<p>GrapheneOS adds a user-facing Network permission toggle providing a robust way to
deny both direct and indirect network access to applications. It builds upon the
standard non-user-facing INTERNET permission, so it's already fully adopted by the app
ecosystem. Revoking the permission denies indirect access via OS components and apps
enforcing the INTERNET permission, such as DownloadManager. Direct access is denied
by blocking low-level network socket access.</p>
<h3 id="ad-blocking">
<a href="#ad-blocking">How can I set up system-wide ad-blocking?</a>
</h3>
<p>The recommended approach to system-wide ad-blocking is setting up domain-based
ad-blocking as part of DNS resolution. You can do this by
<a href="#custom-dns">choosing a Private DNS (DNS-over-TLS) server</a> with support
for blocking ad domains. As an example, AdGuard DNS can be used by setting
<code>dns.adguard.com</code> as the Private DNS domain. In the future, GrapheneOS
plans on adding back <a
href="https://github.com/GrapheneOS/os_issue_tracker/issues/184">an efficient
user-defined blacklist for the local DNS resolver</a>. This feature used to be
included by the project many years ago, but it needs to be reimplemented, and it's a
low priority feature depending on contributors stepping up to work on it.</p>
<p>Apps and web sites can detect that ad-blocking is being used and can determine
what's being blocked. This can be used as part of fingerprinting users. Using a widely
used service like AdGuard with a standard block list is much less of an issue than a
custom set of subscriptions / rules, but it still stands out compared to the default
of not doing it.</p>
<h3 id="ad-blocking-apps">
<a href="#ad-blocking-apps">Are ad-blocking apps supported?</a>
</h3>
<p>Content filtering apps are fully compatible with GrapheneOS, but they have serious
drawbacks and are not recommended. These apps use the VPN service feature to route
traffic through themselves to perform filtering.</p>
<p>The approach of intercepting traffic is inherently incompatible with encryption
from the client to the server. The AdGuard app works around encryption by supporting
optional
<a href="https://kb.adguard.com/en/general/https-filtering">HTTPS interception</a> by
having the user trust a local certificate authority, which is a security risk and
weakens HTTPS security even if their implementation is flawless (which they openly
acknowledge in their documentation, although it understates the risks). It also can't
intercept connections using certificate pinning, with the exception of browsers which
go out of the way to allow overriding pinning with locally added certificate
authorities. Many of these apps only provide domain-based filtering, unlike the deeper
filtering by AdGuard, but they're still impacted by encryption due to Private DNS
(DNS-over-TLS) and require disabling the feature. They could provide their own
DNS-over-TLS resolver to avoid losing the feature, but few of the developers care
enough to do that.</p>
<p>Using the VPN service to provide something other than a VPN also means that these
apps need to provide an actual VPN implementation or a way to forward to apps
providing one, and very few have bothered to implement this. NetGuard is an one
example implementing SOCKS5 forwarding, which can be used to forward to apps like
Orbot (Tor).</p>
<h3 id="baseband-isolation">
<a href="#baseband-isolation">Is the baseband isolated?</a>
</h3>
<p>Yes, the baseband is isolated on all of the officially supported devices. Memory
access is partitioned by the IOMMU and limited to internal memory and memory shared
by the driver implementations. The baseband on the officially supported devices with a
Qualcomm SoC implements Wi-Fi and Bluetooth as internal sandboxed processes rather
than having a separate baseband for those like earlier devices.</p>
<p>Earlier generation devices we used to support prior to Pixels had Wi-Fi + Bluetooth
implemented on a separate SoC. This was not was not properly contained by the stock OS
and we put substantial work into addressing that problem. However, that work has been
obsoleted now that Wi-Fi and Bluetooth are provided by the SoC on the officially
supported devices.</p>
<p>A component being on a separate chip is orthogonal to whether it's isolated. In
order to be isolated, the drivers need to treat it as untrusted. If it has DMA access
that needs to be contained via IOMMU and the driver needs to treat the shared memory
as untrusted, as it would data received another way. There's a lot of attack surface
between the baseband and the kernel/userspace software stack connected to it. OS
security is very relevant to containing hardware components including the radios and
the vast majority of the attack surface is in software. The OS relies upon the
hardware and firmware to be able to contain components but ends up being primarily
responsible for it due to control over the configuration of shared memory and the
complexity of the interface and the OS side implementation.</p>
<p>The mobile Atheros Wi-Fi driver/firmware is primarily a SoftMAC implementation with
the vast majority of the complexity in the driver rather than the firmware. The fully
functional driver is massive and the firmware is quite small. Unfortunately, since the
Linux kernel is monolithic and has no internal security boundaries, the attack surface
is problematic and a HardMAC implementation with most complexity in the isolated
firmware could be better than the status quo. An isolated driver would be ideal.</p>
<h2 id="day-to-day-use">
<a href="#day-to-day-use">Day to day use</a>
</h2>
<h3 id="updates">
<a href="#updates">How do I keep the OS updated?</a>
</h3>
<p>GrapheneOS has entirely automatic background updates. More details are available in
the <a href="/usage#updates">the usage guide's updates section</a>.</p>
<h3 id="updates-sideloading">
<a href="#updates-sideloading">How do I update without connecting the device to the internet?</a>
</h3>
<p>Updates can be <a href="/usage#updates-sideloading">sideloaded via
recovery</a>.</p>
<h2 id="anti-theft">
<a href="#anti-theft">Does GrapheneOS provide Factory Reset Protection?</a>
</h2>
<p>No, since this is strictly a theft deterrence feature, not a security feature, and
the standard implementation depends on having the device tied to an account on an
online service. The only advantage would be encouraging thieves to return a stolen
device for a potential reward after realizing that it has no value beyond scrapping it
for parts.</p>
<p>Google's Factory Reset Protection ties devices to a Google account using a tiny,
special region of persistent state not wiped by a factory reset. It prevents a thief
from wiping the device to a fresh state for resale without being stuck at a screen for
authenticating with the Google account persisted on the device after wiping.</p>
<p>It would be possible to make an implementation not reliant upon an online service
where the user has the option to enable Factory Reset Protection and is given a seed
phrase required to use the device after wiping data from recovery. However, since this
has no security value and the ability to deter theft is questionable, implementing
this is an extremely low priority.</p>
<p>Providing the option to disable wiping from recovery would be simpler, but would be
incompatible with features designed to wipe data automatically in certain cases. This
will not be implemented by GrapheneOS since it isn't a good approach and it conflicts
with other planned features.</p>
<h2 id="bundled-apps">
<a href="#bundled-apps">Why aren't my favorite apps bundled with GrapheneOS?</a>
</h2>
<p>There are drawbacks to bundling apps into the OS and few advantages in most cases.
Rather than GrapheneOS bundling a bunch of apps, it makes far more sense for users to
install their preferred apps via F-Droid, Aurora Store or other sources. GrapheneOS is
also working on designing and implementing a first party app update system for a first
party repository with higher robustness and security than the existing options. Rather
than bundling apps, it could just offer recommendations as part of an initial setup
wizard. Users have unique needs and preferences and there has to be a very compelling
reason to bundle additional apps with the OS. For example, it's useful to have the
Auditor app available before connecting to the internet (see the
<a href="/install#verifying-installation">installation guide</a> documentation on
this).</p>
<p>Bundling additional apps with the OS can increase attack surface, unless users go
out of the way to disable apps they aren't using. Bundling an app into the base OS is
also painful to reverse, since removing the app without implementing a migration
mechanism will lose user data stored in the app. Some users are also going to take
issue with the choices made by the project or will want to make suggestions for
bundling more apps, and having this as a regular topic of discussion and debate is
unproductive and distracts from the real work of the project. Each bundled app also
increases the size of the base OS, and shipping the app updates as part of the OS
updates results in more overall bandwidth usage. It would be possible to ship only
out-of-band app updates to avoid wasted bandwidth for apps users have disabled, but
then the apps would be temporarily out-of-date and vulnerable to patched security
issues after a factory reset or the user re-enabling them. If the updates aren't going
to be shipped with the OS, it really makes no sense to bundle them.</p>
<p>GrapheneOS is focused on making meaningful improvements to privacy and security,
and bundling assorted apps into the OS is not only usually outside of that focus but
often counter to it.</p>
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