Wi-Fi on a Galaxy S20 fails for settings reasons more than hardware ones. Samsung's Adaptive Wi-Fi and Switch to mobile data features move the phone off a weak Wi-Fi network, which looks like drops, so check Settings, Connections, Wi-Fi, Advanced. Forget the network and rejoin it, since a stale profile gives a connected network with no internet. Restart the router. The S20 supports 2.4 and 5 GHz, and a router that merges the two can leave the phone on the weaker band. If Wi-Fi stopped after an update, wipe the cache partition, and as a last step reset network settings.
The checks in more detail
Test the phone on another network or a hotspot to learn whether the phone or the router is at fault. If the S20 connects but the internet is slow, try changing the DNS to a public server in the network's advanced settings, and check whether a VPN or Private DNS setting is active. Samsung's Wi-Fi diagnostics under Device care can also test the connection. Moving a few steps nearer the router and checking the signal bars gives a quick answer on whether distance is the cause, and a restart of the phone clears a radio that got stuck after sleeping overnight.
Because the S20 is a 2020 phone on its last software release, no newer Wi-Fi fix is coming, so the cure lies in settings and in the router. If your router can run the 5 GHz band on a lower channel number, the S20's radio often holds the link better, and a router set to a very wide channel can cause drops that look like a phone fault. Check whether the phone is saving power in a way that cuts Wi-Fi: Settings, Battery and device care, Battery, More battery settings, and look at the options that limit the connection in sleep.
A case with a metal plate or a magnetic mount can weaken the antenna, so remove it for a test. If you share a home with many devices, a router that keeps a long list of leases may refuse the phone; restarting the router clears the list. Finally, an old phone that has had many apps installed over the years may have a background app that uses the network heavily, so look at Settings, Connections, Data usage for an app with a surprising amount of Wi-Fi use.
Differential
Likely causes of “Samsung Galaxy S20 family will not connect to Wi-Fi or keeps disconnecting”, and how to tell them apart
- 1
Switch to mobile data
What separates it The phone leaves Wi-Fi when it is weak
How to confirm Turn it off in Wi-Fi Advanced
- 2
A stale saved network
What separates it Connected but no internet
How to confirm Forget and rejoin
- 3
A router that needs a restart
What separates it Other devices struggle
How to confirm Restart the router
- 4
A merged band name
What separates it Drops at distance
How to confirm Join the 2.4 GHz band by name
- 5
A software fault
What separates it Wi-Fi stopped after an update
How to confirm Wipe the cache partition and reset network settings
Before you touch a setting
Record this first — changing settings destroys the evidence
- Whether other devices work
- The band and signal
- Whether it began after an update
- Whether Switch to mobile data is on
Try in this order
0 of 10 completedCheck Wi-Fi Advanced
ReversibleTurn off Switch to mobile data.
Forget the network
ReversibleRejoin with the password.
Restart the router
ReversibleUnplug for thirty seconds.
Try the other band
ReversibleJoin by its own name.
Wipe the cache partition
ReversibleFrom recovery mode.
Reset network settings
ReversibleLast.
Run Wi-Fi diagnostics
ReversibleSamsung Members, Phone diagnostics, Wi-Fi, to test the radio and the signal.
Check VPN and Private DNS
ReversibleTurn off any VPN and check Settings, Connections, More connection settings, Private DNS.
Try a different DNS server
ReversibleIn the network's settings choose a manual IP and a public DNS and see whether pages load faster.
Check the signal where you sit
ReversibleCompare the phone's Wi-Fi signal bars next to the router and in your usual seat, because a large difference means coverage, not settings, is the cause.
Model-specific
What is true of this model and not of its siblings
- Adaptive features
- Samsung's features can move the phone off Wi-Fi.
- Hotspot test
- A phone hotspot separates phone from router.
- Slow versus down
- A connected network with slow pages points at DNS or the router.
- Diagnostics
- Samsung's diagnostics test the radio quickly.
- Hotspot
- A phone hotspot separates the phone from the router.
- Overnight sleep
- A phone left on a weak network overnight can leave its radio in a bad state until it restarts.
Stop boundary
When this stops being a self-service repair
- !If Wi-Fi fails on every network after a reset, contact Samsung
- !If the router is the issue, ask its maker
- !A phone that finds no networks needs service
Evidence ledger
Sources behind this answer
Exact questions
Common questions
Why does my S20 drop Wi-Fi?+
Switch to mobile data or a weak signal.
Will a reset delete my data?+
No.
Does the S20 support 5 GHz?+
Yes.
Should I forget the network?+
Yes, it clears a stale profile.
Why is Wi-Fi slow on my S20?+
DNS, a VPN or a weak signal.
Does Private DNS matter?+
A misconfigured one can block pages.
Does restarting the router help?+
Often, since routers that run for weeks slow down.
Does the S20 have Wi-Fi 6?+
Yes, the S20 supports Wi-Fi 6.
Can a case weaken the Wi-Fi?+
A metal plate or magnetic mount can.
Will a router restart help?+
It clears stale leases and often fixes a phone that will not join.