Custom ROM glossary

Custom ROM

A replacement Android operating system built from sources like AOSP, flashed in place of the version your phone shipped with.

AOSP

The Android Open Source Project — Google's open codebase that nearly every custom ROM is built on top of.

Codename

The short internal name every device has (Pixel 7 = panther). ROMs are organised by it — how to find yours.

Bootloader

The low-level code that starts your phone. It must be unlocked before you can flash a custom ROM — which typically wipes the device, so back up first.

Recovery

A small separate environment for installing updates and wiping data. Custom ROMs are usually flashed from a custom recovery.

TWRP

Team Win Recovery Project — a popular custom recovery with a touch interface. Some modern ROMs ship their own recovery instead.

fastboot

A mode (and PC tool) for sending commands to the bootloader — used to unlock it and flash partitions over USB.

ADB

Android Debug Bridge — a PC tool for talking to a running phone over USB, e.g. to sideload a ROM or read its codename.

GApps

Google Apps — the Play Store and Google services, packaged separately so you can add them to a ROM that ships without them.

Vanilla

A build with no Google services at all — clean AOSP. You add GApps yourself, or go without.

MicroG

An open-source, privacy-friendly reimplementation of Google's services, used as a lightweight alternative to GApps.

OTA

Over-the-air — an update delivered to the phone directly, so you can upgrade without a PC.

A/B partitions

A layout with two system slots, so updates install to the inactive one and you can roll back if a boot fails. Common on newer phones.

dm-verity

An Android integrity check that can complain after flashing. ROM install guides explain how to handle it for your device.

Official / Unofficial / EOL

ROM status labels — what they mean.

Got the basics? Search your phone to see which ROMs support it.