Reference

Every answer Plain Air can give

The 24 things Plain Air can tell you about your Wi-Fi, what each one means, and the 14 changes it may suggest.

This list is made from the same file the app ships, so it is always exactly what Plain Air says. The sentence at the top of Check is the first of these that applies. An n stands for a number measured on your Mac.

When something is off

Wi-Fi is off. Turn it on in Control Centre, then check again. What to change: Turn Wi-Fi on (on this Mac).
This network wants you to sign in before it lets you online. Open the sign-in page, then check again. What to change: Sign in to this network (on this Mac).
Your Wi-Fi is working, but your router can’t reach the internet. Your router answers in n ms; nothing beyond it does. What to change: Restart your router (on your router); Tell your provider (with your provider).
Plain Air couldn’t get an answer from your router. It ignored pings and connections on ports 53, 80 and 443. The internet times below are still right.
Your Wi-Fi signal is weak here: −n dBm. A Mac starts looking for another access point below −75 dBm. What to change: Move closer to your router, or move the router (on this Mac, when the signal isn’t strong).
Your Wi-Fi signal is only n dB above the noise. Something nearby is drowning it out, or the router is far away. What to change: Move closer to your router, or move the router (on this Mac, when the signal isn’t strong).
Your Wi-Fi is quick, but it pauses on a beat, about every n s. n of n replies from your router took over 40 ms, up to n ms. That’s enough to make calls stutter. What to change: Find what is pausing your Wi-Fi (on this Mac, when AirDrop’s radio link is on); Move closer to your router, or move the router (on this Mac, when the signal isn’t strong).
Your Wi-Fi pauses now and then. n of n replies from your router took over 40 ms, up to n ms, with no regular rhythm. What to change: Find what is pausing your Wi-Fi (on this Mac, when AirDrop’s radio link is on); Move closer to your router, or move the router (on this Mac, when the signal isn’t strong).
Your router is slow to answer: n ms on average. Your own router should answer in a few milliseconds. What to change: Restart your router (on your router); Move closer to your router, or move the router (on this Mac, when the signal isn’t strong).
Your Wi-Fi is fine. The trouble is your internet: Apple takes n ms to answer. That’s n ms beyond your router. What to change: Tell your provider (with your provider).
Your Wi-Fi and internet are fine, but looking up names takes n ms. Every new site waits that long before it starts to load. What to change: Restart your router (on your router); Use a different DNS server (on this Mac).
n networks overlap your channel n. Channel 1, 6 or 11 has n. On 2.4 GHz only channels 1, 6 and 11 don’t overlap. What to change: Move your router to channel 1, 6 or 11 (on your router).

Also worth knowing

Things worth knowing that aren’t a fault. On Check they appear under Also worth knowing, unless one is the first that applies.

Your Mac is using Ethernet or another connection, so there’s no Wi-Fi to check. Your internet and names are still timed.
You’re on 2.4 GHz. A strong 5 GHz network is here too. If it’s your router’s, 5 GHz is usually faster and less crowded. What to change: Join your router’s 5 GHz network (on this Mac).
Your router uses a 40 MHz channel on 2.4 GHz. Apple recommends 20 MHz on 2.4 GHz: wide channels there overlap almost everyone. What to change: Set 2.4 GHz to 20 MHz (on your router).
Your network uses older security: WEP, WPA, WPA/WPA2 or open. Apple recommends WPA3, or WPA2/WPA3 if older devices need to join. What to change: Switch to WPA3 (on your router).
Your router is on a radar channel: n. If radar is heard, it must move off it and stay off for 30 minutes, which you’d see as a short drop. What to change: Think about leaving channel n (on your router).
Location Services is off on this Mac. Apple recommends it for Wi-Fi, so your Mac uses the right channels and power for your country. What to change: Turn Location Services on (on this Mac).
You’re connected through a VPN. Times to the internet include the VPN’s own journey. What to change: Compare with the VPN paused (on this Mac).
Your router doesn’t answer pings, so the Wi-Fi stretch is timed another way. Plain Air times a connection to it instead. Nothing to do.

After Test Speed

Only when you press Test Speed, from the rating Apple’s own test gives.

Your line slows down a lot when it’s busy. Apple’s test rates its responsiveness Low: calls and games may be unreliable while someone downloads or backs up. What to change: Tell your provider (with your provider).
Your line is fast, and mostly holds up when it’s busy. Apple’s test rates its responsiveness Medium: calls may pause for a moment while others use the line.
Your line is fast and stays responsive when it’s busy. Apple’s test rates its responsiveness High.

When all is well

Your Wi-Fi and your internet are both fine. Nothing to change. Check again whenever something feels slow.

What to change, step by step

Each change says what to do, why, and where. Plain Air never makes the change itself: its button only opens the place.

Find what is pausing your Wi-Fi

Most likely to help, on this Mac, offered when AirDrop’s radio link is on. Your router replies in n ms most of the time, then takes up to n ms. AirDrop’s radio link is on, and it borrows the Wi-Fi radio from time to time.

Open Control Centre and set AirDrop to Contacts Only.
Come back and listen again in Pauses.
If the tall lines go, keep it that way during calls.

The button: Open AirDrop settings.

Move closer to your router, or move the router

Most likely to help, on this Mac, offered when the signal isn’t strong. Walls, floors and distance weaken the signal. A router on the floor or in a cupboard reaches less of your home.

Try the same check next to the router.
If it’s fine there, put the router higher and more central.
For a large home, a mesh point halfway between helps.

Source: Apple, Wi-Fi roaming support in Apple devices.

Restart your router

Most likely to help, on your router. It clears a stuck connection to your provider and a slow lookup service.

Unplug the router, or switch it off.
Wait 30 seconds and switch it on.
When the lights settle, check again.

Tell your provider

Most likely to help, with your provider. The trouble is beyond your router, so only your provider can fix it.

Save the Report: it has the times they’ll ask for.
Call or message your provider’s support.
Mention when it started and that your Wi-Fi is fine.

The button: Make a report.

Sign in to this network

Most likely to help, on this Mac. Hotels, trains and cafés often ask you to accept terms before letting you online.

Open the sign-in page.
Accept the network’s terms or enter its code.
Check again.

The button: Open the sign-in page.

Move your router to channel 1, 6 or 11

Most likely to help, on your router. Channels 1, 6 and 11 don’t overlap. Channel 1, 6 or 11 has the fewest strong neighbours here.

Open your router’s settings.
Find Wi-Fi, 2.4 GHz, Channel.
Choose 1, 6 or 11, or Auto if it keeps the channel clear.

The button: Open your router’s settings. Source: IEEE 802.11, 2.4 GHz channel plan (20 MHz channels 5 MHz apart; 1, 6 and 11 do not overlap).

Set 2.4 GHz to 20 MHz

Apple recommends, on your router. Wider channels on 2.4 GHz overlap almost every neighbour.

Open your router’s settings.
Find Wi-Fi, 2.4 GHz, Channel width.
Choose 20 MHz.

The button: Open your router’s settings. Source: Apple, Recommended settings for Wi-Fi routers and access points.

Join your router’s 5 GHz network

Worth knowing, on this Mac. 5 GHz is usually faster and less crowded than 2.4 GHz, if it reaches you.

Open the Wi-Fi menu.
If your router has a separate 5 GHz name, choose it.
Check again here.

The button: Open Wi-Fi settings. Source: Apple, Recommended settings for Wi-Fi routers and access points.

Switch to WPA3

Apple recommends, on your router. Older security is easier to break into, and some new devices won’t join it.

Open your router’s settings.
Find Wi-Fi, Security.
Choose WPA3 Personal, or WPA2/WPA3 if older devices need to join.

The button: Open your router’s settings. Source: Apple, Recommended settings for Wi-Fi routers and access points.

Think about leaving channel n

Worth knowing, on your router. Radar can make your router move off it for 30 minutes. Channels 36 to 48 never have to move.

Open your router’s settings.
Find Wi-Fi, 5 GHz, Channel.
Choose 36, 40, 44 or 48, or keep Auto if you’ve seen no drops.

The button: Open your router’s settings. Source: ETSI, EN 301 893: 5 GHz RLAN (radar detection, DFS).

Turn Location Services on

Apple recommends, on this Mac. Apple recommends it so your Mac uses the right channels and power for your country. It also lets Plain Air show your network’s name.

Open System Settings › Privacy & Security.
Turn on Location Services.
Under System Services, keep Networking & Wireless on.

The button: Open Location Services. Source: Apple, Recommended settings for Wi-Fi routers and access points.

Use a different DNS server

Worth knowing, on this Mac. Your Mac can ask another server to look up names if your router’s stays slow.

Open System Settings › Network › Wi-Fi › Details.
Choose DNS and add a server your provider or IT team recommends.
Check again.

The button: Open Network settings.

Turn Wi-Fi on

Most likely to help, on this Mac. Plain Air can only check Wi-Fi while it’s on.

Open Control Centre.
Turn on Wi-Fi and join your network.
Check again.

The button: Open Wi-Fi settings.

Compare with the VPN paused

Worth knowing, on this Mac. If the internet is slow only through the VPN, the trouble is the VPN, not your Wi-Fi.

Pause or disconnect the VPN.
Check again.
Turn it back on afterwards.

Where the lines are

A reading is called out only when it crosses one of these lines.

Signal: under −75 dBm. Weaker than where a Mac starts looking for another access point. Source: Apple, Wi-Fi roaming support in Apple devices.
Signal: under −67 dBm. Fine for browsing; calls may start to suffer. Source: Apple, Wi-Fi roaming support in Apple devices.
Above the noise: under 15 dB. The signal is barely above the noise.
Above the noise: under 25 dB. Enough for most things; the link slows down.
A reply from your router: over 40 ms. A reply from your own router this slow is a pause on your Wi-Fi.
Slow replies from your router: over 10%. More than 1 reply in 10 over the slow-reply line.
Your router’s usual reply: over 30 ms. Your router itself is slow to answer.
Replies lost from your router: over 1%. Replies from your own router are going missing.
Your internet, beyond your router: over 150 ms. Time added beyond your router, past the one-way limit for calls. Source: ITU-T, G.114: One-way transmission time.
Replies lost from Apple: over 2%. Replies from the internet are going missing.
Looking up a name: over 200 ms. Looking up a name takes long enough to notice on every new page.
A neighbour’s signal: over −80 dBm. A neighbour this strong competes for airtime.
Strong neighbours overlapping your 2.4 GHz channel: over 5 networks. More than five strong neighbours overlapping your 2.4 GHz channel.
How far a 5 GHz network is below yours: under 10 dB. A 5 GHz network within this much of yours is probably reachable from here.