WhatsApp chats live on your phone, not on WhatsApp's servers — lose the phone without a backup and the chats are gone. The good news: both platforms have free built-in backup, and a phone switch done in the right order takes about fifteen calm minutes.
Android: back up to Google Drive
1. Open WhatsApp → ⋮ menu → Settings → Chats → Chat backup. 2. Choose the Google account, set “Back up to Google Drive” to Daily (or Weekly), and decide on videos (they inflate backups hugely — most people leave videos off). 3. Tap Back up now for a fresh copy. 4. For real security, enable End-to-end encrypted backup and store its password somewhere safe — without it, not even Google can read the backup; with it forgotten, you cannot restore it either.
iPhone: back up to iCloud
1. WhatsApp → Settings → Chats → Chat Backup. 2. Tap Back Up Now; turn on Auto Backup (Daily) and decide on videos. 3. The backup counts against your iCloud storage — the free 5 GB fills fast, which is the most common reason iPhone WhatsApp backups silently stop. Check Settings → [your name] → iCloud if backups seem stale.
Restoring on the new phone — order matters
1. On the new phone, sign in to the same Google account (Android) or Apple ID (iPhone) first. 2. Install WhatsApp and verify with the same phone number. 3. When WhatsApp offers to restore from the backup it found, tap Restore — this offer appears once, during setup. Declining it and continuing cannot be undone later without reinstalling. 4. Wait for messages to restore, then media follows in the background.
Switching between Android and iPhone
WhatsApp supports direct transfer during setup of the new phone: on Android-to-iPhone use Apple's Move to iOS flow; on iPhone-to-Android use the cable/transfer option offered in the new Android phone's setup (Samsung and Pixel setups handle this well). This is a device-to-device transfer — the cloud backups above do not cross platforms. Do it during the new phone's first setup; it is much harder afterwards.
Local backups (Android bonus)
WhatsApp also keeps local backups on the phone (Internal storage → WhatsApp → Databases) for the last 7 days. Copying that folder to a computer is a free extra safety net before any risky operation — and the only option if Google Drive backup is failing.