One of the many reasons I made the switch from PC to Mac a few years ago was the constant frustration of cryptic connectivity error messages on Windows. The laptop I used frequently would lose its Internet connection, and do little to help me understand why. Macs are not without their own connectivity issues, but I've found that understanding and fixing them is much more straightforward.
The most important place to start in troubleshooting your Wi-Fi problem is isolating the source. Is your router to blame, or your Mac? The simplest way to figure this out is simply to check the connection on another Wi-Fi-connected device like an iPad, smartphone, or even another computer. If that device is also having problems connecting, then you need to start with the router. I've found that the majority of router problems can be solved with the simple-yet-effective "reset" solution. Some routers just need to be turned off and on again.
Today, we are looking at fixing connectivity issues on your Mac, so if the problem is isolated to your router and a reset didn't work, I unfortunately have to direct you either to your favorite search engine or to your router's manual.
The Wi-Fi Icon in Your Menubar
Conveniently, OS X will show you what your wireless status is via a dynamic icon in the menubar. The icon is a dot with three expanding lines above it. With a strong wireless signal, all the bars are black. As the signal weakens, fewer lines are filled.
A full icon like the one above indicates full signal strength.
If you don't see this icon, head over to Finder > Applications > System Preferences. Click on Wireless settings, then click the "Show Wi-Fi status" option.
Make sure your Wi-Fi status is shown in your menu bar.
If that icon is greyed-out, that means you aren't connected to a wireless network. Click on it and it will reveal a list of networks that are nearby. You should have already set one up, or know of a neighbor who unwittingly allows others to use his or her unsecured Wi-Fi. Either way, selecting your desired network will connect you (or first prompt you for the password, if it is protected).
Now, if only one line on the Wi-Fi icon is filled (indicating low-signal strength), you may be too far away from the router. You can improve signal strength by moving closer, or by installing another router in your home to act as a wireless bridge.
Another possible Wi-Fi icon is the exclamation mark. This indicates a password problem. Understanding this issue requires a basic explanation of Wi-Fi security. There are two common types of encryption, WEP and WPA/2. WEP, which stands for Wireless Equivalent Privacy, has largely been eliminated due to well-known security exploits that make it very easy to hack. WPA and WPA2 are much more secure, and consequently, more commonly used today.
If you are having trouble connecting to a secured WEP network, you may need to make some slight changes to the password that your network administrator (or Starbucks barista) gave you. If the password is ASCII, such as password12345, you'll need to add quotation marks to the beginning and end, so that the password reads "password12345". If the password is hexadecimal, you'll need to add a dollar sign to the beginning.
Good Signal Strength, Slow Connection
Just as there are periodic advancements in cell-phone network technology, Wi-Fi networks have been improved over the years. The 802.11 is the name of the wireless technology used by Wi-Fi routers, and has evolved to become faster and more reliable. There are several variants of the 802.11 standard, each with a letter tacked on. These include a, b, g, n, and others that are currently being developed. At the moment, 802.11n is the fastest and most commonly used.
Network Utility can help you find out whether your Mac is taking advantage of the fastest possible Wi-Fi technology.
If you're having issues streaming video from sources such as YouTube or Netflix despite subscribing to a fast Internet service such as cable, the bottleneck might be your router settings. The best way to see if your Mac is using 802.11n is to use OS X's Network Utility. Go to Applications > Utilities, and find Network Utility. The first tab, called "Info," is what we want. Select Wi-Fi and take a look at the bottom of the window. If you don't see the letter "n" then you either don't have a Mac capable of using the technology, or you need to install the 802.11n enabler from Apple.
While distance from the router and the use of old Wi-Fi technology may be slowing your connection, you might also be feeling the effects of signal interference. There are a variety of appliances and gadgets in your house that could be affecting the signal, including microwaves, power lines, wireless speakers, etc.
The problem in such a situation is that your computer and router are operating on a channel that other devices are using. Apple routers, for instance, utilize the 2.4 and 5 GHz bands. If one of these bands is causing problems, simply resetting your router will force it to try using the other band in order to avoid interference.
DNS and TCP/IP Problems
When you type a web address into your browser, say www.google.com, that address gets converted into a series of numbers (called an IP address). Rather than being forced to memorize every website's IP address, a Domain Name Server (DNS) takes care of that database for you. If you can't seem to pull up any websites despite your Mac telling you that you are connected to the Internet, you may need to check to make sure that your DNS settings are correct.
You should see something in the DNS tab.
To do this, we will need to open up System Preferences > Network > Advanced, then select the DNS tab. You should see at least one entry in each of the two columns. If you don't, you'll need to call your Internet Service Provider (ISP).
Next we can check your Transmission Control Protocol/Internet Protocol (TCP/IP) settings. TCP/IP is a set of protocols that manage how data is transferred between computers on a network. Click on the tab just to the left of DNS within the Advanced network settings menu. Here you'll find a whole slew of strange numbers and acronyms.
Check your TCP/IP settings to make sure you have an IP address.
While it is possible that your computer's network settings have been set up in a specific way that deviates from standard settings, your window should look pretty similar to what mine looks like here, (although your IPv4 address will be different). If you don't see anything for your IP address, click on the button to the right that reads "Renew DHCP Lease."
Tip: Also try using your Mac's built-in troubleshooting tools to help diagnose your connectivity problem: Airport Utility and Network Diagnostics.
The advice above covers the most typical issues that you'll run into regarding your Mac's web connectivity. Once again, if the connectivity problem stretches across multiple devices, contact your Internet Service Provider and make sure your router is functioning properly. If the problem is isolated to a single machine and the techniques above had no impact, stop by your local Genius Bar and see if they can provide any insight.