Why Your Mac's Wi-Fi Is Slow (and How to Diagnose Whether It's the Mac or the Network)

You’re on a Zoom call, your MacBook Pro stutters, and your iPhone — sitting two feet away on the same network — runs a 400 Mbps speed test like nothing’s wrong. That’s the moment most people start blaming the router. Don’t yet. Slow Wi-Fi on a Mac usually has one of about six causes, and you can isolate which one in under ten minutes.

This guide walks through the fix sequence that actually works on macOS 14 Sonoma and 15 Sequoia, on both Apple Silicon and Intel Macs. We’ll use a couple of Terminal commands the Mac genius bar never tells you about, plus the new Wi-Fi diagnostics buried inside System Settings.

Step 1: Confirm the Mac is the bottleneck

Before you touch a single setting, prove the Mac is the problem. Run a speed test on the Mac (fast.com is fine), then run the same test on an iPhone or iPad on the same Wi-Fi network, standing in the same room. Note both numbers.

• If both devices are slow → it’s the network, the router, or the ISP. Stop here and reboot the router.
• If only the Mac is slow → continue with this guide.
• If the Mac is slow only on certain websites → it’s likely a DNS issue. Skip to our DNS troubleshooting guide.

While you’re at it, check what speed your Mac is actually negotiating with the router. Hold the Option key and click the Wi-Fi icon in the menu bar. Look at the “Tx Rate” line. On a modern 802.11ax (Wi-Fi 6) network, you should see values like 1200 Mbps, 2400 Mbps, or higher. If you’re seeing 72 Mbps or 144 Mbps, your Mac has fallen back to legacy 802.11n — that’s a clue.

Step 2: Use wdutil to get the real diagnostics

Apple hides the most useful Wi-Fi tool inside the Terminal. Open Terminal and run:

sudo wdutil info

You’ll get a wall of text covering the Wi-Fi interface, current SSID, channel width, PHY mode, MCS index, RSSI, and noise floor. The key fields:

• PHY Mode: should read 802.11ax on a Wi-Fi 6 router. If it shows 802.11ac or 802.11n, your Mac isn’t using the fastest protocol available.
• Channel: 2.4 GHz channels are 1-11; 5 GHz channels are 36, 40, 44, 48, 149, 153, 157, 161; 6 GHz starts at 1 (Wi-Fi 6E only on M2 Macs and newer).
• Channel Width: 80 MHz or 160 MHz means good throughput. 20 MHz on 5 GHz means trouble.
• RSSI: -50 to -65 dBm is great, -65 to -75 dBm is fine, below -75 dBm is poor.
• Noise: closer to -100 dBm is better. -85 dBm or higher means interference.

If the Mac connected to a 2.4 GHz band when a 5 GHz band was available, that’s a clue too. Some routers broadcast both bands under one SSID and let the client choose; Macs occasionally make the wrong choice and stick with it for hours.

Step 3: Forget the network and rejoin it

This sounds dumb. It’s also what fixes the problem 40% of the time, because macOS caches the negotiated channel, security mode, and IP lease, and sometimes that cache goes stale.

1. Open System Settings → Wi-Fi.
2. Click Details next to your network name.
3. Scroll down and click Forget This Network. Confirm.
4. Wait five seconds, then rejoin from the Wi-Fi menu and re-enter the password.

After rejoining, run sudo wdutil info again and check whether the PHY Mode and channel changed. Often they will — and your speeds will jump.

Clear the cruft that confuses macOSSweep wipes leftover network helpers from old VPNs and adapters that can interfere with Wi-Fi performance. Get Sweep free →

Step 4: Check what’s hogging the connection

A slow connection isn’t always a slow link — sometimes it’s a fast link being saturated by something you forgot was running. Open Activity Monitor → Network tab. Sort by “Sent Bytes” and “Rcvd Bytes” descending.

Common culprits:

• Photos: iCloud Photo Library uploading 40 GB of recent imports.
• Time Machine: backing up to a network drive while you’re trying to work.
• Backblaze / Carbonite: catching up on a missed nightly backup.
• Dropbox / OneDrive / Google Drive: indexing or uploading.
• Steam / Epic / App Store: downloading game updates in the background.
• mDNSResponder: occasionally goes haywire after a network change. If it’s pegged, restart it with sudo killall -HUP mDNSResponder.

Quit or pause whatever’s at the top of the list, then re-test. If your speed shot up, you found it.

Step 5: Reset the SystemConfiguration cache

macOS stores network state in /Library/Preferences/SystemConfiguration/. After a major macOS update, these files occasionally end up with stale entries pointing to networks, VPNs, or adapters that no longer exist. Deleting them forces macOS to rebuild from scratch.

1. Turn Wi-Fi off from the menu bar.
2. Open Finder → Go → Go to Folder, paste /Library/Preferences/SystemConfiguration/.
3. Move these files to the desktop (don’t delete them yet — you want a backup):
   • com.apple.airport.preferences.plist
   • com.apple.network.identification.plist
   • com.apple.wifi.message-tracer.plist
   • NetworkInterfaces.plist
   • preferences.plist
4. Restart your Mac.
5. Turn Wi-Fi back on. Rejoin your network with the password.

If everything works after a few hours, drag the desktop copies to the Trash. If something broke, drag them back.

Step 6: Check the channel your router is using

If your wdutil readout shows a 5 GHz channel like 36 or 40, you’re probably fine. If it shows channel 149 or higher in a region where DFS (Dynamic Frequency Selection) channels are crowded, you might be sharing airtime with neighbors’ routers, weather radar, or military systems.

Free apps like WiFi Explorer Lite (Mac App Store) and NetSpot scan all bands and show you which channels are clogged. If channel 149 has fourteen other networks on it and channel 36 has two, log into your router and switch.

There’s a faster waySweep does the cleanup in seconds — leftover network configs, stale VPN profiles, and orphaned helper tools. Try Sweep free →

Step 7: The location trick most people don’t know

macOS supports network “Locations” — saved profiles you can switch between. Creating a fresh location bypasses every cached setting tied to your current one without touching anything else.

1. System Settings → Network.
2. Click the three-dot menu near the top right → Locations → Edit Locations.
3. Click + to add a new one. Name it “Test.” Click Done.
4. Apple menu → Location → Test.
5. Rejoin Wi-Fi.

If speeds are normal in the Test location, your Automatic location had something corrupted. You can either keep using Test or go back to Automatic and start trimming services from it.

Step 8: Check for software that hooks the network

VPN clients (NordVPN, ExpressVPN, Mullvad, Cisco AnyConnect, Tailscale), corporate device management agents (Jamf, Mosyle, Kandji), and some firewalls (Little Snitch, LuLu) install network extensions that intercept all traffic. If one of them is misbehaving, every packet pays a tax.

Check what’s loaded:

systemextensionsctl list

Quit any VPN clients you’re not actively using. Disable Little Snitch’s filtering temporarily (alert mode → off). Re-test.

If a VPN is uninstalled but its extension is still loaded, that’s a classic stuck-state. The extension and its leftover prefs can keep slowing things down even though the app is gone. This is one place where Sweep helps: it surfaces orphaned launch agents, login items, and preference files from apps you’ve already deleted, so you can clean up the trail without hunting through ~/Library/LaunchAgents by hand.

Step 9: When it really is the router

If you’ve worked through everything above and your iPhone is still faster than your Mac on the same network, focus on these:

• Router firmware: outdated firmware breaks Wi-Fi 6 negotiation with newer Macs constantly. Update it.
• Mesh systems: eero, Orbi, and Deco occasionally route a Mac to a far satellite even when the main router is closer. Reboot the satellites.
• 2.4 GHz / 5 GHz split SSIDs: if your router lets you, give the 5 GHz band its own SSID and connect the Mac to that one specifically.
• DHCP lease: a cluttered DHCP table sometimes causes weird routing. Reboot the router.

When to give up and call the ISP

If ping 1.1.1.1 from Terminal shows latency over 100 ms with packet loss, and it does so on every device on the network, the problem is upstream of you. That’s an ISP call.

Most slow-Wi-Fi-on-Mac complaints aren’t router problems and aren’t ISP problems. They’re cached state on the Mac. The wdutil command, a fresh location, and a clean SystemConfiguration folder will solve the vast majority of cases. Add a sweep of leftover VPN extensions and old network helpers from apps you uninstalled months ago, and you’ve covered the rest.