Fortunately your MacBook comes with a number of useful tools for diagnosing network issues, plus there are a handful of third party tools that give you even more information.
Summarise Your Current Connection

A lot of Mac users don’t know this, but OS X comes with some fairly advanced wireless monitoring tools out-of-the-box. You just need to know where to find them. You probably know that if you click the Wi-Fi icon in the menubar, you’ll get a list of nearby wireless networks.

Here’s a useful trick: hold the option key, then click the Wi-Fi icon in the menubar. You’ll see a lot more information about the network you’re currently connected to.

There’s many things your Mac’s option key can do, but this one is really useful for seeing a summary of your current network. Here’s what all this information means, starting from the top:

    IP Address: Your computer’s IP on the local network.
    Router: The IP of the router on the local network. You’ll need this if you want to configure your router.
    Internet: Lets you know if Internet access is available over the current network or not.
    Security: Outlines the kind of encryption used by the network you’re currently connected to.
    BSSID: The MAC (media access control) address of the router you’re connected to, useful for identifying access points on a network with more than one.
    Channel: The frequency your router is using. You might want to change this if there’s too much interference.
    Country Code: Tells you which nation the router was designed to work in. Different countries use slightly different frequencies, depending on radio regulations.
    RSSI: Received signal strength indication, a way of measuring how powerful the signal currently is.
    Noise: A way of measuring how much other signals are interfering with your Wi-Fi connection
    TX Rate: The max speed you can expect with your current signal.
    PHY Mode: The type of connection your router is offering.
    MCS Index: Can be used to calculate the maximum bandwidth of your current connection.

That’s quite a bit of information, all easy to access with just a keystroke and a click. But if you want more, you don’t have to look very far: a world of data is just a few keystrokes away.
See Information About Other Nearby Networks

Click the Wi-Fi icon again while holding the option key, but this time click Open Wireless Diagnostics.

This will open an app primarily designed to help guide you through difficulties with your wireless connection.

Instead of following the steps, however, click Window in the menubar, then click Scan. This will open a window that lets you see all the information we saw above, but for every network visible your Mac can detect. Your current connection can be seen in bold.

There’s a lot of ways you can use this information, particularly if your Wifi signal is currently weak or regularly dropping out. To start: if there are too many networks using the same channel in one area, interference is going to be high.

Speaking of interference: if you want to get an idea of where in your house the signal is seriously being interfered with, click Window in the menubar again, then click Performance. You’ll get a realtime monitor:

Walk around and you can see how your movement affects performance. You want to keep the rate, quality and signal high, and the noise as low as possible. It’s neat, but let’s keep going down this rabbit hole and find even more information.
Third Party Apps Offer Even More Information

The tools included with OS X give you access to all sorts of key points, but if you want even more there are a number of third party tools out there that can help you learn even more.

For example: NetSpot is free for non-commercial use, and gives you access to more information than the above methods.

Unlike Apple’s included tool, this will continue to scan every visible network every 10 seconds. This means you can walk around and see where your signal is weakest, and which other networks are causing interference. The Signal To Noise ratio indicator is a big help here, because you can quickly ascertain how the signal changes as you walk around.

And it gets better: as we’ve outlined before, you can actually walk around and make a map of your Wi-Fi signal. This helps you find weak points that you can address by changing your router’s channel, moving your router, or using a Wi-Fi extender.

There are some other programs worth checking out too:

    WiFi Radar Pro, offers a simple interface for a lot of the above information — $12, with a free trial.
    iStumbler, in addition to WiFi, also detects Bluetooth signals —$25, with a free trial.
    Kismac2 is an open source Mac tool for scanning networks. We’ve mentioned it’s now-abandoned predecessor before. There currently isn’t a stable version available, and a trial resulted in more than a few problems, but so far it’s a very powerful tool that we could easily see ourselves checking out once the bugs are worked out — free.

How Do You Scan Wireless Connections On Your Mac?

These are the best Wi-Fi tools we’ve found for the Mac, but we’re always amazed at what our readers manage to find. So we want to know: what tools have you used to improve your Mac’s Wi-Fi signal?

And while you’re thinking about Wi-Fi, why not read up on how to see if someone’s stealing your Wi-Fi, or how to hide your WiFi network. Though, of course, the above methods will reveal hidden Wi-Fi networks, which kind of makes hiding them feel pointless, but you get the idea.