Estimates suggest a large majority of replaced phones end up in drawers rather than being sold, given away or recycled. Several better options exist.
First: wipe it properly
Sign out of your accounts before factory resetting. On both platforms, a device still linked to an account is locked to it and unusable by anyone else – which protects you if stolen and makes the phone worthless if sold.
Remove the SIM. Then factory reset. Modern phones encrypt storage by default, so a reset is genuinely sufficient.
Sell it
Even several generations old, phones retain value. Trade-in programmes are convenient and typically pay less than selling directly.
Check the value before assuming it is worthless. The gap between what people assume and what phones actually fetch is large.
Give it away
An old phone is a working device for someone who has none. Several charities redistribute them, and domestic violence services in particular accept phones for emergency use.
Keep it as a backup
Genuinely useful. A spare phone with a charged battery covers the situation where your main one breaks or is stolen, and that situation is common enough to plan for.
It also works as a dedicated device – a music player, a satellite navigation unit for the car, a camera for a child, a webcam.
Recycle it properly
If it is genuinely dead, it contains recoverable metals and materials that should not go to landfill. Manufacturers and retailers operate take-back schemes and most areas have collection points.
What not to do
The drawer. A battery degrades while stored, so the phone is worth less every year it sits there, and eventually it is worth nothing.