Have an Apple, Mac, or iOS tech question? Here's the answer. This time in Ask, we'll let you know what to do when your Mac's monitor refuses to run at the desired resolution.
My 27-inch Dell Ultrasharp monitor has been acting up. It’s been fine for 18 months, but recently I got a new MacBook Pro and now I can’t get it to display at full resolution. It is stuck at 1280 x 768, which is smaller than it used to be on my old Mac!
The monitor hardware is probably fine. It’s more likely to be a problem with the EDID (Extended Display Identification Data) configuration — EDID is a way for monitors to tell your graphics card the best way to format images for that particular screen.
Some Dell monitors don’t list their native resolution properly, and if your graphics card driver doesn’t override this value, you can be stuck at 1280 x 768 or 1360 x 765. Open System Preferences > Display and hold Option while you click the “Scaled” button. This shows all the display resolutions that your graphics card can output, and you can manually force 2560 x 1440.
From the Display Preferences, you should be able to manually force the resolution you're looking for.
If the monitor still won’t cooperate, you’ll need to use an EDID override file. These are just text files, but creating one for yourself from scratch is a tall order. Fortunately there are override files for Dell monitors located here.