On a Galaxy S25 Ultra the Wi-Fi fault is most often Wi-Fi 7 with WPA3. Owners in Samsung's forums reported the phone disconnecting and falling back to mobile data on a Wi-Fi 7 plus WPA3 router while a Wi-Fi 6 plus WPA2 setup held, speeds dropping to 1 Mbps or even 0, and the problem persisting after One UI 8. Two fixes came up repeatedly: turn off Intelligent Wi-Fi, and switch on Wi-Fi Safe mode, which took one owner from 600 Mbps to 1200 Mbps. Test a WPA2 or Wi-Fi 6 network name first.
Differential
Likely causes of “Samsung Galaxy S25 family will not connect to Wi-Fi or keeps disconnecting”, and how to tell them apart
- 1
Wi-Fi 7 with WPA3 on the router
What separates it The phone disconnects periodically and uses mobile data; a Wi-Fi 6 with WPA2 network works
How to confirm An owner's thread describes exactly this pairing; join a WPA2 or Wi-Fi 6 network name to test
- 2
Intelligent Wi-Fi switching networks
What separates it The connection stalls when the phone tries to move to a better network
How to confirm Turning off Intelligent Wi-Fi, Switch to better Wi-Fi networks and prioritize real-time data solved it temporarily for some
- 3
Wi-Fi Safe mode off
What separates it The phone connects at half the speed the router offers
How to confirm One owner saw 600 Mbps until enabling Wi-Fi Safe mode, then 1200 Mbps
- 4
Randomised MAC address
What separates it The router keeps forgetting the phone
How to confirm Switching the network to Phone MAC was a suggested fix
Before you touch a setting
Record this first — changing settings destroys the evidence
- The router's Wi-Fi standard and security, for example Wi-Fi 7 with WPA3
- Whether the phone falls back to mobile data when it drops
- The link speed shown in the network's details
- Whether other devices hold the same network
Try in this order
0 of 5 completedTry a WPA2 or Wi-Fi 6 name
ReversibleJoin a network set to WPA2 or Wi-Fi 6 for a day. If the drops stop, the Wi-Fi 7 plus WPA3 pairing is the cause.
Turn off Intelligent Wi-Fi
ReversibleOpen Settings, Connections, Wi-Fi, Advanced, Intelligent Wi-Fi and switch off Switch to better Wi-Fi networks.
Try Wi-Fi Safe mode
ReversibleEnable it in Wi-Fi's advanced settings if it is offered, and compare the link speed.
Use Phone MAC
ReversibleOpen the network's settings and change MAC address type to Phone MAC.
Force restart
ReversibleHold Power and Volume down for about 10 seconds to reload the radio firmware.
Model-specific
What is true of this model and not of its siblings
- Wi-Fi
- GSMArena lists Wi-Fi 7 and Bluetooth 5.4 for the S25 Ultra.
- Other models this page answers
- These steps also fit the Galaxy S25+.
Stop boundary
When this stops being a self-service repair
- !If it drops on every network, including a WPA2 Wi-Fi 6 one, run Samsung Members diagnostics and contact Samsung support
- !If only one router is affected, update its firmware or ask the maker about Wi-Fi 7 with WPA3
Evidence ledger
Sources behind this answer
Restart, update, forget the network, Safe mode, reset and router checks.
Owners reporting slow Wi-Fi and the Wi-Fi Safe mode result.
Owners reporting disconnections.
Wi-Fi 7 and Bluetooth 5.4.
Exact questions
Common questions
Is the S25 Ultra's Wi-Fi 7 the problem?+
Owners in Samsung's EU forum report drops on Wi-Fi 7 with WPA3 that a Wi-Fi 6 with WPA2 network does not have.
Why is my S25 Ultra Wi-Fi so slow?+
Some owners in the threads saw 1 Mbps or 0 Mbps, and one doubled a 600 Mbps link by enabling Wi-Fi Safe mode.