System Preferences

Why Do Some Mac Apps Need to “Control This Computer Using Accessibility Features?”

Some apps, like Dropbox and Steam, will ask to “control this computer using accessibility features.” But what the heck does that even mean?

The wording is confusing, to say that least. What does this permission actually grant? Basically, this gives the app in question the ability to control other programs. Apple outlines their advice here:

If you’re familiar with an app, you can authorize it by clicking Open System Preferences in the alert, then selecting the checkbox for the app in the Privacy pane. If you’re unfamiliar with an app or you don’t want to give it access to your Mac at that time, click Deny in the alert.

But that just leaves more questions. Why do you have to give this permission at all? What does giving this permission mean—will such applications really “control this computer”? And why is this called “Accessibility” access, instead of just system access? Let’s break this down.

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Why Do I Have to Do This?

The process of enabling Accessibility Settings is a bit convoluted. You need to open System Preferences, then head to Security & Privacy > Privacy > Accessibility. From there you need to click the lock icon in the bottom-left corner, enter you password, and only then can you grant your application access.

So why do you have to do this? The answer, in short, is to protect your security.

By default, Mac apps are self-contained, and can’t change the way you interact with the system or other applications. This is a very good thing. It prevents sketchy things from happening, like games you’ve downloaded logging your keystrokes or malware clicking buttons in your browser.

But some applications need to control other applications to…

Save Space on Your Time Machine Drive by Excluding These Folders From Backups

Are you getting notifications about a full Time Machine drive? Do you feel like your backups are taking too long? A bigger, faster hard drive might be the best solution, but you can also help by excluding particular folders from your backups.

We’ve shown you how to back up and restore files with Time Machine, including how to exclude particular folders from being backed up. To exclude a folder, just head to System Preferences > Time Machine > Options.

Some more options will slide down, giving you the ability to exclude particular folders from your backups. But which folders can be safely disabled? And are any disabled by the system already? Let’s take a look.

What Does Time Machine Exclude By Default?

Time Machine already excludes a bunch of things you don’t need backed up: your Trash, caches, and indexes. And you know how you can use Time Machine even if your drive isn’t plugged in? The local backups that make that possible are also not backed up, as that would be redundant. So you don’t need to worry about excluding system-level things like logs and caches—Time Machine already has you covered.

If just knowing that system-level stuff is already excluded is enough for you, go ahead and skip the rest of this section. But if you’re interested in seeing the complete list of folders excluded by default (or just want to prove to yourself that something is excluded), here’s how to do it.

A file named “StdExclusions.plist” outlines everything that Time Machine excludes. You can find that file in the following location:

/System/Library/CoreServices/backupd.bundle/Contents/Resources/

You can quickly open that file by running the following command in the Terminal (which you can find at Applications > Utilities > Terminal):

/System/Library/CoreServices/backupd.bundle/Contents/Resources/StdExclusions.plist
The list is too long to include here, so you should just check it out yourself.

Individual programs can also mark particular files to not be backed up. Typically, this includes caches and other temporary files. You can find a list of these exempt files by running the following command in the Terminal:

sudo mdfind "com_apple_backup_excludeItem = 'com.apple.backupd'"

To summarize, though, you don’t need to worry about stopping Time Machine from backing up caches or your Trash folder, because it already knows not to. And a big thanks to Brant Bobby on Stack Exchange for pointing out the commands that prove this.

What Other Items Should I Consider Excluding?

Now that you’ve seen what Time Machine excludes by default, let’s take a look at some of the other items you might consider excluding to free up some space.

Your Dropbox Folder, or Any Folder You’re Already Syncing

If you’re using Dropbox, OneDrive, Google Drive, or any other syncing service, you already have those files stored in at least two locations—on your local drive and in the cloud. If you’re syncing files to other devices, as well, then you have those files stored in other locations as well.

Just be careful. Most cloud services offer a grace period to recover deleted files. Dropbox, for example, gives you 30 days, and keeps older versions of the files it has—just like a backup. But if your cloud service does not provide this feature, you probably don’t want to exclude those files from your Time Machine backup, since…