WhatsApp for Samsung Galaxy Note 9

On a phone this old, random shutdowns are almost always the aging battery losing its ability to hold voltage under load, so it cuts out even when the charge indicator still shows power left. First boot into Safe Mode (press and hold the power button, then long-press the 'Power off' icon) to rule out a misbehaving app, and clear the cache partition from recovery mode. If it still cuts out, the battery has degraded and needs replacing; a swollen or worn cell is the most common culprit. Samsung's built-in 'Battery and device care' diagnostics can confirm reduced battery condition. See how others solved this on Reddit

One UI's battery optimization is almost always the cause. Go to Settings > Apps > WhatsApp > Battery and set it to Unrestricted so the app isn't put to sleep in the background. Then confirm Settings > Apps > WhatsApp > Notifications is on, and inside WhatsApp under Settings > Notifications make sure the message and group tones are enabled. Turning off 'Adaptive battery' under Settings > Battery and device care > Battery > More battery settings also keeps WhatsApp from being throttled overnight. See how others solved this on Reddit

Android's per-app notification channels let you do this on the system side: open Settings > Apps > WhatsApp > Notifications, tap a category like Messages or Group notifications, then choose Sound to pick a unique tone. WhatsApp's own Settings > Notifications also lets you set separate tones for messages, groups and calls. Individual chats can override these from the chat's menu under Custom notifications. See how others solved this on Reddit

Samsung Music scans any folder that doesn't contain a .nomedia file. Use the My Files app to open Internal storage > Android > media > com.whatsapp > WhatsApp > Media > WhatsApp Voice Notes (and WhatsApp Audio), then create an empty file named .nomedia inside it. Reboot or rescan, and those clips disappear from your music library. The same .nomedia trick works for any other folder you want hidden from media apps. See how others solved this on Reddit

The Note 9 still runs current WhatsApp fine, but it's capped at Android 10 (One UI 2) and never received newer versions, and Meta periodically raises WhatsApp's minimum supported Android version, so a 'this version is no longer supported' warning will arrive eventually. To keep it usable, install WhatsApp only from the Play Store (never a modified GBWhatsApp build, which risks getting your number banned), keep a current backup under WhatsApp Settings > Chats > Chat backup to Google Drive, and replace the worn battery. It's perfectly serviceable for messaging today, but plan an upgrade before the OS cutoff catches up to it. See how others solved this on Reddit