CalyxOS

CalyxOS is an operating system for smartphones based on Android with mostly free and open-source software. It is produced by the Calyx Institute as part of its mission to "defend online privacy, security and accessibility."

CalyxOS preserves the Android security model, using Android's Verified Boot system of cryptographic signing of the operating system, and running with a locked bootloader, partly thanks to an installer that guides the user through the process of unlocking and then re-locking the bootloader.

History
The Calyx Institute annual reports state CalyxOS was publicly launched during their 2018–2019 fiscal year. Inspiration included Tails and Qubes OS, and goals were said to be "completely open source", removing proprietary Google tracking, and including apps Tor, Signal and CalyxVPN for increased privacy.

CalyxOS supports Google Pixel smartphones Pixel 3 and newer. CalyxOS supports Fairphone 4. In March 2024, CalyxOS Fairphone 5 is officially supported.

In April 2022, CalyxOS announced support for OnePlus 8T, 9, and 9 Pro. However, in May 2022, CalyxOS announced OnePlus builds were pulled because of a bootloader "relock issue". As of July 2022, according to CalyxOS the OnePlus relock issue had not been resolved.

In May 2024, CalyxOS supports Pixel all types 3 - 8, Fold and Tablet, Fairphone 4 - 5, Moto G32 - G52 and Shiftphone SHIFT6mq.

Software
CalyxOS ships with MicroG as an open-source alternative to the Google Mobile Services, including Mozilla Location Services as an optional replacement to the location services provided by Google, but gives the user the option to disable microG and its location services.

Reception
In October 2020, Moritz Tremmel reviewed CalyxOS. A month later, Tremmel explained why he preferred CalyxOS over LineageOS. A year later in September 2021, Tremmel further explained how CalyxOS was different from other ROMs because it did not require as much "fiddling". Rahul Nambiampurath, writing for MakeUseOf in March 2021, termed CalyxOS, "[one of the] best [Android] ROMs for privacy ... offers the perfect middle ground between convenience and privacy". In August 2021, Android Authority wrote CalyxOS "puts privacy and security into the hands of everyday users."

In 2022, the book c't Sicher ins Netz: How to block out monitors and attackers, said "CalyxOS is one of the youngest custom ROMs, it will only celebrate its second birthday in summer 2022. With a built-in Datura firewall, VPN and Cloudflare DNS, Calyx promises more security than some other mobile systems."

In 2023, CalyxOS was the one alternative phone operating system recommended by Carey Parker in the book "Firewalls Don't Stop Dragons".

In a review in February 2023, the Kuketz Security blog said CalyxOS "offers a coherent overall package that should give users who want to (strongly) reduce their dependency on Google a good start" and said the integrated Datura Firewall works well. However, it criticized some previous delayed security updates and said the website does not "quite match what the present analysis revealed" regarding the information given to Google.