How to back up your Android phone before flashing

Flashing wipes the phone

Two steps in the process erase your data: unlocking the bootloader — required to flash on most phones — forces a full factory reset, and a clean install wipes the data partition again. Anything only stored on the phone, not synced or copied off, is gone. Do every backup below before you unlock.

What to back up

Work through this list. The first items are obvious; the last one catches most people out.

• Photos, videos and files — copy your internal storage to a computer, or sync it to a cloud or NAS you control.
• Contacts and calendar— export them to a .vcf/.ics file, or sync to an account you'll still have after flashing.
• Messages— SMS and app chats (Signal, WhatsApp) aren't kept unless you export them; each app has its own backup.
• App data— most apps don't back up automatically without Google. Note the logins you'll need to redo, and export anything you can.
• Two-factor (2FA) codes — authenticator apps do not survive a wipe. Export your codes first or you can be locked out of your accounts. This is the one people forget.

How to save it

The simplest reliable backup is a copy of your internal storage on a computer: plug in over USB, switch the connection to file transfer, and drag the folders across. For contacts, use the Contacts app's export. On a deGoogled ROM, Seedvault gives you an encrypted system backup to a folder or cloud you choose. For 2FA, open each authenticator and use its export or transfer feature before you wipe — and print your accounts' one-time recovery codes as a fallback.

Keep a way back

Backups protect your data; a recovery plan protects the phone. Before flashing, download a known-good build you can return to — your current ROM, or the manufacturer's stock firmware — and make sure you know how to enter fastboot/recovery. If a flash fails, that is what gets you booting again.