How to Fix WiFi Not Working After a macOS Update: Keychain, Network Profiles, and Adapter Fixes

A macOS update should make your Mac faster and more secure — but it routinely breaks WiFi for a significant number of users. The culprit is almost always corrupted network preference files or stale Keychain password entries that the installer overwrites or damages. Here’s how to systematically fix it, from the quickest two-minute reset to the nuclear option of wiping all network configuration.

Why macOS Updates Break WiFi

macOS stores WiFi settings in a handful of .plist files inside /Library/Preferences/SystemConfiguration/. An update that modifies these files — or writes new versions that conflict with what was already there — can corrupt saved networks, DHCP leases, and security credentials. Separately, the Keychain stores your WiFi passwords: if the update invalidates the stored credential, macOS will silently fail to authenticate, showing you as “connected” but delivering no internet.

Fix 1: Forget and Rejoin the Network (2 Minutes)

The fastest first step. Go to System Settings → Network → Wi-Fi, click the three-dot menu next to your network name, and choose Forget This Network. Turn WiFi off, wait 10 seconds, turn it back on, and reconnect by entering your password fresh.

This forces macOS to create a new Keychain entry and pull a fresh DHCP lease — and it resolves roughly half of all post-update WiFi failures.

Fix 2: Renew Your DHCP Lease

If you’re connected but have no internet (or see a “self-assigned IP” warning in the status bar), your DHCP lease is stale. Go to System Settings → Network → Wi-Fi → Details, click the TCP/IP tab, and hit Renew DHCP Lease. Your Mac will request a fresh IP address from the router.

A self-assigned IP (169.254.x.x) means your Mac got no response from the DHCP server. This is common after updates because macOS briefly resets the network stack during installation and can miss the lease renewal window. For more on this error, see our guide on WiFi connected but no internet.

Fix 3: Delete the Keychain Entry

If macOS keeps asking for your WiFi password repeatedly — or connects then immediately drops — a corrupted Keychain entry is almost certainly the cause.

1. Open Keychain Access (Spotlight → “Keychain Access”).
2. In the search bar, type your WiFi network name (SSID).
3. Right-click the entry with Kind: AirPort network password and choose Delete.
4. Confirm deletion, then reconnect to your network and enter the password manually.

This creates a fresh Keychain entry and usually fixes authentication loops immediately. If you see multiple entries for the same SSID, delete all of them before reconnecting.

Fix 4: Delete Corrupted Network Preference Files

If the quick fixes above didn’t work, the underlying .plist configuration files are likely corrupted. Open Finder, press Cmd + Shift + G, and navigate to /Library/Preferences/SystemConfiguration/. Move these files to your Desktop as a backup, then restart:

• com.apple.airport.preferences.plist
• com.apple.network.identification.plist
• NetworkInterfaces.plist
• preferences.plist

macOS regenerates all four files from scratch on the next boot, giving you a clean network configuration. You’ll need to rejoin your WiFi networks and re-enter passwords afterward.

Fix 5: Flush the DNS Cache via Terminal

If you can connect to WiFi and ping IP addresses but websites won’t load, the DNS resolver cache is likely corrupted. Open Terminal (Spotlight → “Terminal”) and run:

sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

Enter your admin password when prompted. This purges the DNS cache and restarts the mDNSResponder daemon without a reboot. Pages should load normally within seconds.

Fix 6: Create a New Network Location

macOS “Locations” are saved sets of network settings. If yours got corrupted during the update, creating a new one bypasses the problem entirely without touching individual preference files:

1. Go to System Settings → Network.
2. Click the Location dropdown at the top and choose Edit Locations…
3. Click the + button, name the new location (e.g., “Home”), and click Done.
4. Reconnect to your WiFi network under the new location.

Fix 7: Reset NVRAM and SMC (Intel Macs)

On Intel MacBooks, the System Management Controller (SMC) handles low-level hardware including the WiFi adapter. A corrupted SMC state after a major update can cause the adapter to report as unavailable or drop intermittently.

Reset NVRAM

Shut down your Mac, then power on and immediately hold Option + Cmd + P + R for about 20 seconds until the Mac restarts a second time (you’ll hear the startup chime twice on older models, or see the Apple logo appear and disappear twice on newer Intel Macs).

Reset SMC on T2 MacBooks

Shut down, hold Ctrl + Option + Shift for 7 seconds, then add the Power button and hold all four keys for another 7 seconds. Release, wait a few seconds, then power on normally. Apple Silicon Macs (M1, M2, M3, M4) do not have an SMC — a standard restart achieves the same reset.

Check for Third-Party Software Conflicts

VPN clients, firewall apps (Little Snitch, Lulu), and antivirus tools hook into the macOS network stack at a low level. If they were not updated alongside macOS, they can silently block all traffic while showing your WiFi as connected. Temporarily disable or uninstall these utilities and test WiFi without them. Re-enable one by one to isolate the culprit. See our guide on WiFi disconnecting with a VPN active for more detail on resolving these conflicts.

Quick Checklist

• Forget the network and rejoin with a fresh password entry
• Renew DHCP lease if you see a self-assigned IP (169.254.x.x)
• Delete the Keychain entry for your SSID in Keychain Access
• Move the four .plist files out of /Library/Preferences/SystemConfiguration/ and restart
• Flush DNS with sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder
• Create a new Network Location in System Settings
• Reset NVRAM and SMC on Intel Macs
• Disable VPN clients and firewall apps temporarily to rule out conflicts

Once your connection is restored, run a speed test to confirm you’re getting the full bandwidth your plan provides — sometimes clearing a corrupted network configuration also removes background throttling and delivers noticeably better speeds.