Fairphone 4

Overview

codename FP4	🛡️
Flavor (?):	Slim
Android:	13
First released:	2025-05-30
Firmware:	included
Encryption (?):	FBEv2
Relockable:	yes
VerifiedBoot/AVB (?):	v2.0
Patchlevel (?):	Platform + Kernel (Firmware until 2025-11)
Verified & tested by:	The AXP.OS community
State:	stable

Installation guide

You want to switch between flavors or coming from DivestOS?

Please read this first: All about AXP.OS flavors If you miss a flavor you can request it here.

Known issues

AXP.OS - Known Issues
Issue tracker - won’t fix

Specific for your device:

Knowledgebase: FP4

Boot modes

Each device has its own method to access special boot modes.
See: FP4 (@LineageOS wiki)

Firmware

AXP.OS for the Fairphone 4 includes the appropriate bootloader and modem firmware for the corresponding Android version provided.

Important

Unfortunately, some manufacturers enable so-called “Anti-Rollback Protection” (ARB), which in the worst-case scenario can even take effect within the bootloader (notable examples include various LG models, as well as Samsung and even some Google Pixel devices).

In these cases, special caution must be exercised, as this can often result in a hard brick, which may be unreparable depending on the manufacturer and model. This is not a problem with AXP.OS itself, but affects all custom OSes for such devices.

If you are unsure, please check with the support room before flashing AXP.OS.

Install / Upgrade

Install (A/B)

Setup AXP.OS

Follow Setup

Re-locking the bootloader

Follow Bootloader-Lock

Fingerprint information

On boot you may see a fingerprint/ID verifying AVB trust.
Some devices show only 8 chars, others full digest.
See more details here.

This fingerprint is unique per device and flavor.

If you see a different ID, immediately request support.

Slim build

BOOTLOADER minimal ID
        272DE007

BOOTLOADER full ID:
        272DE00712A447F3
        4AC484EB5E9A1A28
        3217A7174855F2EE
        1A4E16C591592826

XDA thread

See here

Debugging

DEVICE-BOOT-DEBUG-PATH: /metadata
See Logs

Download

All downloads have a GPG signed sha512sum file which should be used to verify the download & file integrity.
Details how to make use out of it can be found here.

💡 The hashsum of new builds are also send in the sfX Automation channel. This gives you a second and independent option for comparison if the download server is compromised.

Flavor (what's this?)	OS zip	Recovery image	AVB key (what's this?)	Release key (what's this?)
Slim 🛡️	(click)	(click)	(click)	(right click, save-as)
	(click)	(click)	(right click, save-as) click here for info

Last updated on 2026-03-31

Fairphone 3