Those who use external Bluetooth devices with a Mac, whether it's a keyboard, mouse, headset, or anything else, are probably aware that connection strength between the device and the computer is going to directly impact how usable the device is.
If your Bluetooth device connections seem flakey, or if your wireless keyboard or mouse isn't as responsive as you think it should be with your Mac, there is a easy way to check Bluetooth signal strength in macOS. Simply Option (Alt) click the Bluetooth menu bar item, then move the mouse cursor over the Bluetooth item you want to check the signal strength for and look for "RSSI".
RSSI (Received Signal Strength Indicator) can be a bit weird to read, but essentially a higher number means a better connection, and a lower number means a worse connection. Note however that the numbers are negative, so that may read opposite to what you'd expect. For example, a connection of -45 is significantly stronger and better than a connection of -100, which is weaker and more likely to have issues. The rough guidelines below may help read the connection, though the precise signal you get is going to vary on other factors we’ll discuss below:
-40 to -55 is a very strong connection
-70 and above represents a good connection
-100 and below represents a bad connection
-110 and below is almost unusable
The two most likely reasons for a bad Bluetooth connection are low batteries and heavy interference from something in the environment. Batteries are easy to test, all you need to do is swap in a new set of batteries or charge the device in question and see if the RSSI increases and if the device becomes more stable. Environmental factors can be trickier to track down, but if you see a huge drop in the RSSI when you move a headset behind a fireplace for example, you can surmise that something in the wall is causing the interference and you should rearrange the equipment accordingly. It's also vaguely possible that the device itself has a defective antenna, though that’s fairly rare for most quality devices.
In general, applications in macOS are packaged into a ".app" bundle that appears to be a single file but is actually a self-contained folder. Unlike Windows, in which an application usually installs a folder that contains the executable and supporting files, most of what an macOS app needs to run is stored within the .app bundle. Deleting an application bundle will remove that application's binary and all the supporting files contained within. Many apps, however, also install additional files in the user's Library folder, such as application preferences and caches.
To manually remove an macOS app, make sure the app is closed and head to the user's Library folder (in OS X Lion and above, hold down the Option key while selecting the Go menu from the Finder's menu bar and select Library). Here, you'll want to check for references to the application in the Application Support, Caches, LaunchAgents, and Preferences folders. Remove any files or folders that you are certain belong to the application you're trying to uninstall. You may also want to check the main Library folder by navigating to the top level of your hard drive and opening the /Library folder, although most applications will confine their files to the user-specific Library. Due to sandboxing requirements imposed by Apple, apps obtained from the Mac App Store are even easier to remove. Simply delete two items: the application file itself from the Applications folder and the application-specific folder in ~/Library/Containers (user's Library folder).
Another way to remove macOS apps is to use third-party tools. Take note, however, that automated tools can sometimes miss certain files or folders, and users employing these tools should always perform a manual check to ensure that all remnants of the application have indeed been removed. Finally, some applications (such as Cocktail) have their own uninstaller. Wherever possible, use the application-specific uninstaller for these applications.
Regardless of which method you choose, remember that leaving behind the occasional abandoned preference file is not likely to cause harm or performance issues. In general, removing the app bundle from the Applications folder and a file or two from the user's Library folder is enough to remove the application from the drive and free up disk space.
One of the scariest things that can happen to your Mac is a failure to turn on at all. You press the power button and nothing happens - no startup sound, no light, nothing. If this happens, you can check several things before hauling your Mac to the nearest Apple Store for repair.
First, trace the entire flow of electricity to your Mac. Check your Mac's power cord to ensure it is firmly seated where it connects to the computer as well as where it plugs into the wall. If it goes through an outlet strip or a UPS, make sure that's also connected and turned on. Also check that any surge protectors are still working - a power surge might have knocked them off. You can confirm that an outlet is good by plugging in something else, such as a light. If the outlet and all cable connections check out, make sure the power cord has no crimps, breaks, or other damage.
Once you've established that your AC power path is good, it's time to look at your Mac itself. Unplug everything you can - not the power cord, your mouse and keyboard if they're wired, and your monitor if it's not built in - but disconnect everything else and try pressing the power button again. If your Mac turns on, you know that one of your peripherals was at fault.
If your Mac doesn't turn on, it's worth trying to reset your Mac's SMC (System Management Controller), a chip that manages a number of hardware functions - including the operation of the power button. Directions vary by Mac model; see Apple's instructions for details (http://support.apple.com/kb/ht3964).
If you have a Mac laptop, its battery should last through most power outages, so you may not notice that you have a power-related problem until the battery runs out, at which point your Mac might simply appear to be dead. So try all the above tips, but also check your power adapter. If you have an AC cable attached to the adapter (as opposed to a plug going directly into the wall), make sure that cable is securely connected. If you have access to another AC adapter, switch to it briefly - that will tell you whether the original adapter is bad or whether it's something in your Mac itself.
Still no luck? In that case, it's time for professional help. An Apple Store or authorized repair center should be able to diagnose and fix the problem.
Did you know that you can quickly access information about your router, and check if your network is performing well? See your BSSID, signal-to-noise ratio, and even the transmit rate between your router and computer. All it takes is a press of a button and a click of your trackpad/mouse.
If you hold down the Option (alt) key and click the Wi-Fi icon in the menu bar, it will provide you with details about your router and the network you're using. The items in gray (except for "Wi-Fi: On") are all pieces of additional information seen only in this mode.
• IP Address: This is your computer's IP address.
• Router: Your router's IP address. You can type this into your browser to access your router's web interface.
• Internet: This tells you if you are able to access the internet or not. If not, open Wireless Diagnostics.
• Security: Your router's security. Most routers on the market offer WPA2 Personal, and it keeps your network encrypted.
• BSSID: This is your router's MAC, or hardware address. It acts as an identifier for your router that lets it talk to other network-connected devices.
• Channel: This is your WLAN channel, and it determines which radio frequency the router uses to transmit information.
• RSSI: Received Signal Strength Indicator measures how well a device "hears" a signal from the router. It's useful for determining if you have enough signal to get a good wireless connection.
• Noise: This measures how much radio noise is interfering with the RSSI signal. Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power, often expressed in decibels.
• TX Rate: The transmit rate is the speed of the data that is transmitted between your router and your computer. Right now I have a speed of 450 Mbps.
• PHY Mode: This is the wireless protocol that the router uses, according to the IEEE 802.11 wireless standard.
• MCS Index: This number corresponds to the protocols uses to encode the radio signal.
Apple makes it very easy to back up your Mac using Time Machine, so there is no excuse not to create a Time Machine backup before installing macOS Sierra.
Follow these steps to back up your Mac using Time Machine.
• Connect an external hard drive to your Mac. Choose a new hard drive, or one that you don't mind erasing.
• An alert may appear asking if you want to use the drive to backup your Mac. If so, Use as Backup Disk.
• If not, open System Preferences > Time Machine and click Select Backup Disk. Choose the external drive.
• Switch Time Machine to On.
• A progress bar will appear in the Time Machine system preference pane. Wait for the Time Machine backp to complete before continuing with the macOS Sierra installation.
Follow these instructions to install the macOS Sierra update on your Mac.
• Once you've backed up your Mac, launch the App Store (located in /Applications/App Store) and search for macOS Sierra.
• Click Download to initiate the download, and fill out your Apple ID information if prompted. Download progress will appear in your Purchases tab.
• Once the download has finished, you'll see a macOS Sierra installer launch. Follow the on-screen instructions to finish installing the software update, which should take around half an hour depending on the spec of your Mac.