Mac Wi-Fi keeps dropping or crawling? Find the cause, fix it

First, measure

Before you change anything, find out what's actually wrong. Two commands, both built into your Mac, do most of it. Open Terminal (⌘ Space, type Terminal, Return) and run:

% networkQuality

==== SUMMARY ====
Uplink capacity:    40.351 Mbps
Downlink capacity:  321.310 Mbps
Responsiveness:     Medium (110 ms | 543 RPM)
Idle Latency:       29 ms

A full speed test — it can take a minute, so let it finish (or press Control-C to stop it). “Downlink capacity” is your real download speed. “Responsiveness” is how well the connection holds up when it's busy — that's what makes video calls stutter, even when the speed looks fine.

Then check the signal itself — how strong and clear it is:

% system_profiler SPAirPortDataType

Current Network Information:
  <your network>:
    PHY Mode: 802.11ax
    Channel: 36 (5GHz, 80MHz)
    Signal / Noise: -49 dBm / -94 dBm
    Transmit Rate: 1020

A healthy reading: the signal (-49) is strong, you're on the faster 5 GHz band, and there's little background noise to fight through. (The old airport command was removed in a recent macOS version.)

The signal number (measured in dBm) works like a loudness dial for your Wi-Fi — but it counts in negatives, and closer to zero means louder and clearer. The -49 above is excellent. Around -60 is still strong; -70 to -80 is faint, and you'll get drops; below -80 barely works. If the “noise” number climbs close to the signal, other devices are drowning your router out — that's interference, not distance.

A crowded channel

Slow at busy hours, or fine in one room and bad in the next — even with full bars.

Wi-Fi is split into channels, and into two bands — the older 2.4 GHz and the faster 5 GHz. When you and a dozen neighbors crowd the same channel, or your Mac is stuck on the slower 2.4 GHz band, your Mac can barely pick your router out of the crowd, and everything drags. The Channel line in the reading above tells you where you are: 1, 6, or 11 is 2.4 GHz; 36 or higher is 5 GHz.

Fixmove onto the faster 5 GHz band if your router offers one — it usually shows up as a separate network name. Or change your router's channel to a less crowded one. Getting onto 5 GHz is usually the single biggest improvement.

NoahNoah checks how crowded your Wi-Fi is and tells you, in plain words, when that's the problem. One real fix took a Mac's download from 23 to 212 Mbps — same room, same router.

A weak signal

Drops when you move rooms; slower the farther you get from the router.

Wi-Fi fades fast through walls, floors, and appliances. Once the signal gets too faint, your Mac keeps re-sending the same data, and eventually gives up and disconnects.

Fixmove closer to the router, or move the router out into the open — off the floor, out of a cabinet, away from the microwave. In a big house, adding a mesh point does more than any setting.

It's not the Wi-Fi — it's the lookup

Pages hang on “Connecting…”, then load fast once they start. Speed tests look normal.

Every time you open a site, your Mac first has to look up where that site actually lives — turning a name like apple.com into a numbered address, the way you'd look up a phone number before dialing. That step is called DNS, and when it's slow, every page stalls before it even starts, even though your connection is fine. To check, compare a numbered address against a name:

% ping -c 5 1.1.1.1

64 bytes from 1.1.1.1: icmp_seq=0 ttl=55 time=17.9 ms
64 bytes from 1.1.1.1: icmp_seq=1 ttl=55 time=17.6 ms
...
round-trip min/avg/max = 16.8/18.3/21.6 ms

This talks straight to an address — no lookup involved. About 18 ms here means the connection itself is healthy.

% ping -c 5 apple.com

64 bytes from 17.253.144.10: icmp_seq=0 ttl=56 time=18.1 ms
64 bytes from 17.253.144.10: icmp_seq=1 ttl=56 time=19.4 ms
...
round-trip min/avg/max = 14.0/18.4/20.9 ms

This one goes through the lookup — also ~18 ms, so the lookup is fine here. If it were much slower than the address above (or hung on the name), the lookup would be your problem.

Fixgive your Mac a faster lookup service: System Settings > Wi-Fi > Details > DNS, and add 1.1.1.1 or 8.8.8.8 at the top. Then clear out the old one:

% sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

Clears your Mac's saved lookups so the new setting takes hold. Asks for your password; nothing permanent changes.

NoahIn one real session Noah found the lookup taking 206 ms — the hidden reason pages were loading blank — on a connection that otherwise tested fine, and switched it to a faster one.

An old connection in the way

Every new connection stalls for a few seconds before it works.

Your Mac keeps a list of ways to get online — its service order — and tries them top to bottom. If a dead one sits at the top — an old USB adapter, a leftover VPN, a virtual machine — your Mac tries it first every time and waits for it to fail before falling back to Wi-Fi. Check the list:

% networksetup -listnetworkserviceorder

The ways your Mac tries to get online, top to bottom. Wi-Fi should be at or near the top.

FixSystem Settings > Network > ••• > Set Service Order…, drag Wi-Fi to the top, and delete anything you no longer use.

NoahNo cleanup app finds this. On one real Mac, Noah traced the hangs to an old T-Mobile USB adapter sitting at the top of that list — the Mac tried it before Wi-Fi and waited for it to fail every single time.

A VPN or filter in the way

Everything is slow, or some sites fail while others work. It started after you installed a VPN or a “privacy” app.

These apps sit between your Mac and the internet and route everything through themselves. A VPN to a far-away server, or a filter that inspects every request, slows the whole connection down.

Fixturn off any VPN or filter you didn't set up on purpose (System Settings > VPN, and Network > Details > Proxies), and disconnect a VPN to test. Also check your browser add-ons — a coupon or “security” extension can quietly slow every page.

A setting gone stale

Only this Mac struggles; every other device is fine. It connects, but nothing loads.

Your Mac saves details about each network it joins. Those details can go bad — often after an update or a new router — and then the Mac connects but can't actually get anywhere.

Fixwork from gentle to firm: renew the address your router gave it (Wi-Fi > Details > TCP/IP > Renew DHCP Lease), then forget the network (Details > Forget This Network) and join it again fresh. Still stuck? Switch Wi-Fi off and on from Terminal:

% sudo ifconfig en0 down && sudo ifconfig en0 up

Turns Wi-Fi off and back on. Check your Wi-Fi's name is en0 first — run networksetup -listallhardwareports.

Interference from other gadgets

Drops at certain moments — when the microwave runs, say.

The 2.4 GHz band shares the air with microwaves, cordless phones, baby monitors, and Bluetooth. When those switch on, they drown your router out.

Fixmove onto the 5 GHz band — it's less crowded, and because it doesn't travel as far, the neighbors and appliances don't reach it.

The router is blocking the Mac

Wi-Fi connects, but the Mac can't reach a printer, HomePod, or shared drive — or a device won't finish setting up.

Some routers are set to keep devices from talking to each other — a feature meant for guest networks. If your Mac and the other device are walled off like that, they simply can't find each other.

Fixput both devices on the same network (not the guest one), and turn off “AP isolation” (sometimes called client isolation) for your main network.

NoahNoah says so plainly. In one case a HomePod wouldn't set up and the Mac was fine — the cause was the router walling the two off from each other. Noah named it, instead of sending the user chasing a Mac problem that wasn't there.

A recent macOS update

Wi-Fi got flaky right after an update.

A big update occasionally ships a Wi-Fi bug, or leaves your old network details in a state it no longer likes.

Fixcheck for a smaller follow-up update (System Settings > General > Software Update) that may already fix it. If not, forget and rejoin the network — an update often spoils the saved details.

When it's the router, not the Mac

Every device in the house is slow, not just the Mac.

Then it isn't a Mac problem at all — it's the router, the modem, or the line coming into your home.

Fixunplug the modem and router for 30 seconds and plug them back in, check the router's app for an update, and make sure your provider isn't down. If a restart helps for a while but it keeps coming back, an aging router or a weak line is usually why.

The short version

1. Run networkQuality — and check whether other devices are slow too.
2. Run system_profiler SPAirPortDataType — check your signal, and move onto 5 GHz.
3. ping an address, then a name — if the name is slower, switch your lookup (DNS) to 1.1.1.1.
4. Check your connection list and any VPN — nothing dead should sit above Wi-Fi.
5. Forget and rejoin the network, renew the address, restart the router.