Why I switched from CalyxOS to GrapheneOS – my custom ROM experience report

Digital sovereignty has long ceased to be a niche topic. With debates about data protection, dependence on other states and the enormous market power of US tech companies growing ever fiercer, many people are asking themselves: How much control do I actually still have over my own data? Smartphones play a central role here – they accompany us around the clock and are deeply integrated into our private and professional lives. Android in particular is often perceived as open and flexible, but a closer look shows: not all Android is the same. In my search for more control and less dependence on US companies, I came across so-called custom ROMs early on. This article is a personal experience report on my journey using a custom ROM, from CalyxOS to GrapheneOS – with all the highs, lows and open questions that come with it.

Not all Android is the same: under the hood, there are big differences between Google's official version and privacy-friendly alternatives such as CalyxOS or GrapheneOS.

Out of curiosity and out of privacy concerns, I switched from the standard Android world to custom ROMs – first CalyxOS, and now I use GrapheneOS on my Pixel 9 and don't want to go back.

A custom ROM is an alternative firmware for Android smartphones that is based on the freely available Android Open Source Project (AOSP), but does not come from Google. Manufacturer ROMs and Google's own Android contain additional services, telemetry and preinstalled apps that collect extensive usage data and are often linked to Google accounts.

• “Android” is only the shared core, but each version can differ massively in tracking, bloatware and security features.
• Custom ROMs such as CalyxOS or GrapheneOS largely remove Google services or encapsulate them to minimize data leakage and give more control over permissions.

It all started with an interview in t3n in which a developer explained that he uses a custom ROM because privacy matters more to him than convenience. Suddenly it was clear: there are alternatives where not every gesture, every location and every app use ends up in some log.

At the beginning of 2021, I bought a Google Pixel 4a 5G and, after some research, chose CalyxOS because it is considered a beginner-friendly, privacy-focused ROM. At the end of 2024, I switched to a Pixel 9 and immediately flashed CalyxOS again – Google hardware, but without Google's standard Android.

“Flashing” is the process of replacing the original operating system with another one – in my case CalyxOS or GrapheneOS. Put simply, you unlock the bootloader, connect the phone to your computer and install new firmware, much like switching operating systems on a PC.

• Google Pixel devices offer official tools and documentation for unlocking and flashing.
• CalyxOS and GrapheneOS optimize their builds specifically for Pixel and provide installation scripts that take a lot of work off your hands.

The installation was much more straightforward than the term “custom ROM” suggests. CalyxOS offers its own web installation tool for Pixel devices, and there are countless step-by-step guides online.

GrapheneOS also provides detailed instructions and a web installer, but it is aimed more at users who are willing to engage more deeply with security.

Instead of Google Play, I mainly use two building blocks: the Aurora Store and F-Droid.

• Aurora Store: Access to apps from the Google Play Store without having to use your own Google account.
• F-Droid: An alternative app store exclusively for free and open-source software, without ads and without built-in trackers.

Unlike the classic Google Play Store, F-Droid puts free licenses and transparency at the center – no personalized ads, no proprietary tracking SDKs.

CalyxOS comes with additional security and privacy features that go beyond standard Android. These include finer control of app permissions and preinstalled privacy tools.

GrapheneOS goes one step further and focuses heavily on hardening, for example through stricter sandboxing and extended memory and network security features. Instead of the Aurora Store, you use the classic Google Play Store here, but (unlike on CalyxOS) it runs in a sandboxed environment.

Mobile payments with Google Wallet didn't work for me on CalyxOS, because the app checks whether a certified Google Android that passes the integrity test is running. Custom ROMs without official certification fail this check, so Wallet blocks the feature.

I experimented with Magisk to get around these checks, but it wasn't reliable – and failed payments at the checkout are simply annoying in everyday life.

Since payment methods via Google Play didn't work for me, I couldn't buy any apps or make in-app purchases in the store. That is frustrating when you want to support developers but don't want to go back into the full Google ecosystem.

In addition, some apps – such as certain mobile accounts like yuh – refused to work because they verify the operating system and only accept original, certified Google Android.

The default camera on CalyxOS and GrapheneOS doesn't quite match the Google Camera of the original ROM, because many AI features such as HDR+ or Night Sight are tied to proprietary Google services. The pictures are solid, but the typical “Pixel look” with automatic optimization is missing.

CalyxOS relies on microG, a free reimplementation of Google Play services, to keep many apps compatible. That is technically impressive, but for me it sometimes led to sluggish update processes.

Occasionally, individual microG components or services had to be reinstalled before everything ran smoothly again – usually just when I urgently needed an app.

In the summer of 2025, the Calyx Institute announced that development of CalyxOS would be temporarily paused – a large banner on the website makes this more than clear. Among others, the institute's founder Nicholas Merrill and the technical lead Chirayu Desai left the organization.

An open letter warned that new installations are not recommended for the time being and that users might temporarily not receive current security patches.

Hardening explained: Hardening means configuring and adapting an operating system or application so that its attack surface is as small as possible. This includes, for example, stricter default permissions, additional security checks, tighter sandboxing for apps and consistently switching off unnecessary functions, so that attackers find far fewer points of attack.

Officially, Android is built on the open-source core AOSP, yet at the same time Google is moving more and more relevant components into proprietary or internally developed areas. In 2025, several sources reported that Google plans to significantly restrict public AOSP development.

New guidelines make life harder for alternative app stores and open-source projects such as F-Droid, for example through mandatory central registration. Nevertheless, projects such as GrapheneOS continue to benefit from the years of groundwork Google has put into the Android core.

I currently use GrapheneOS on my Pixel 9 and have no plans to return to an original Google Android. The system feels focused, tidy and radically secure – even if some convenience is sacrificed for it in places.

One open issue remains mobile payments: I still want to try whether I can find a setup on GrapheneOS that works in everyday life without betraying my privacy standards.