WhatsApp for Samsung Galaxy S6 edge

The S6 edge has 3GB of RAM and TouchWiz/Grace UX aggressively kills background apps, so WhatsApp gets purged and has to reconnect when you reopen it. Open Settings > Apps > WhatsApp > Battery and set it to Unrestricted (on Nougat firmware, go to Settings > Device maintenance > Battery, open the three-dot menu > Settings, and remove WhatsApp from the apps that are put to sleep / add it to the unmonitored apps list). Also disable any RAM-cleaning or 'memory boost' tool, since clearing memory forcibly closes WhatsApp and is the main cause of reconnect delays. See how others solved this on Reddit

Samsung Internet often serves WhatsApp the mobile site, which hides the QR code, so request the desktop version: tap the menu (three lines) in Samsung Internet, then 'Desktop site' (or the PC-monitor icon), and reload web.whatsapp.com. If it still fails, clear the browser cache under Settings > Apps > Samsung Internet > Storage > Clear cache, or just use Chrome instead, since WhatsApp Web is meant to run on a computer browser while your phone stays online and connected. See how others solved this on Reddit

Edge lighting only triggers for apps you explicitly enable, so open Settings > Display > Edge screen > Edge lighting, turn it on, then tap 'Manage notifications' and toggle WhatsApp on. Make sure WhatsApp notifications themselves are allowed under Settings > Apps > WhatsApp > Notifications, and note the glow generally only shows when the screen is off and the phone is face-up, so it won't light up while you're actively using the device. See how others solved this on Reddit

First clean the bottom microphone pinhole, since lint clogging it is the most common cause of low call volume on aging S6 edge units. Then check that no case is covering the mic, and confirm the right mic is active by recording a quick voice note in WhatsApp; if your voice is faint in that recording and across other apps too, the mic module itself may be worn and a repair or replacement is the only real fix on this older hardware. See how others solved this on Reddit

WhatsApp still installs and runs on the S6 edge, but the phone stopped getting security updates years ago, so treat it as a secondary device: factory reset it via Settings > General management > Reset > Factory data reset, then sign in fresh and restore your chat history from Google Drive during setup. Keep only WhatsApp and a browser on it, connect over Wi-Fi, and avoid storing sensitive accounts, since the outdated Android version no longer receives patches. See how others solved this on Reddit

Newer WhatsApp releases require a higher Android version than the S6 edge can run, so the Play Store may show the app as incompatible or refuse to update it. Clear the store cache via Settings > Apps > Google Play Store > Storage > Clear cache, and if updates still fail you can sideload the last compatible APK directly from WhatsApp's official site (whatsapp.com/android); back up your chats to Google Drive first so nothing is lost if you have to reinstall. See how others solved this on Reddit