For privacy-conscious users, third-party accessory makers sell privacy screen filters designed for MacBooks — but are they safe to use on those devices? Privacy screen filters look like the tinted windows of a car or the tinted lenses of sunglasses. Essentially, they suppress the display's brightness and make it harder to view from indirect angles. For example, a person using a laptop at their desk will be able to see their screen fine, albeit more dimmed than usual. However, someone sitting behind or next to them will have a much harder time viewing what's on their screen.
But the construction of MacBooks can make it dangerous to install accessories on the keyboard, palm rests, and display. There's a small amount of space between the top and bottom casing of a MacBook when it closes, so placing something in between could cause a problem when closing the laptop. Anything left inside the MacBook — from a large crumb to a camera cover — can potentially break the screen when it closes. However, Apple does sell privacy screen protectors on its official Apple Store website. That would insinuate that there's no risk of a privacy screen protector inadvertently cracking the MacBook's display.
What Apple Says About Other Accessories
Though Apple doesn't offer any guidance about privacy screen filters specifically, it does provide insight on a few other similar accessories. The company explicitly warns users not to use camera covers on the inside of their MacBooks. The reason for this, Apple says, is that the clearance between the display and keyboard is designed to very tight tolerances. For that reason, closing the laptop with a camera cover protruding from the display could damage it.
But what about other, thinner accessories? Apple says that removable accessories — like palm rests and keyboard covers — should be taken off a MacBook before it's closed. Again, the company cites the tight clearance between the laptop's display and keyboard when closed, and reminds users that leaving something in between could cause damage.
That means that it's probably fine to use a privacy screen filter on a MacBook, but users should take the filter off before closing the device. Some screen filters attach to the MacBook's display with magnets, meaning it can be applied and removed with ease. Using that same logic, permanently applying a privacy screen filter to a MacBook's display with adhesive probably isn't the best idea. Beyond the fact that it could damage the display, there are some lighting situations where a laptop with a screen filter applied would be hard to view. MacBooks have tight tolerances when closed, so be wary of placing anything inside.
Source: Apple Store, Apple Support 1, 2