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Fix Blurry Text on Mac Using External Non-Apple Monitor

After connecting my newly-purchased Mac mini 2018 to my Dell U2410 24 inch 1920×1200 LCD monitor by HDMI cable, I notice that the text is a little blurry and pixelated. The lines aren’t smooth, but jagged. The text looks like it would on an old analog TV.

The problem is caused by the Mac choosing to talk to the Dell monitor using YPbPr, an input color format previously used by S-Video and composite video for analog TVs. The Dell monitor supports two input color formats, RGB (digital computer standard) and YPbPr (analog TV standard). I am not sure why the Mac defaulted to using YPbPr, instead of the superior RGB color format.

Note: I did not see this problem when connecting my MacBook Air 2015 to the Dell monitor using the Apple Mini DisplayPort to DVI adapter. Online comments seem to indicate that this issue only occurs with the 2018 (and probably later) Macs.

The solution is to force the Mac to use the RGB input color format for my Dell U2410 monitor. This is accomplished by creating or overwriting the macOS’s EDID (Extended Display Identification Data) configuration file for the Dell monitor. The details are documented by this webpage, Fixing the External Monitor Color Problem with My 2018 MacBook Pro.

Tip: To verify that YPbPr is being used by your monitor, check the “Input Color Format” in the monitor settings. On my Dell monitor, I go to the monitor’s settings Menu and select “Color Settings” to view the “Input Color Format” field.

Because the EDID override files are located in a protected system directory, “/System/Library/Displays/Contents/Resources/Overrides/”, we will need to use the macOS Recovery Mode to write to it.

Here are the steps I took:

  1. Download the “patch-edid.rb” script file from GitHub’s adaugherity/patch-edid.rb project. This script will create an override EDID file to force RGB usage. Look for the “Download ZIP” button near the top-right. The archive file will be downloaded to “~/Downloads/7435890-00ff3ead17ae77d2f1c376e90831c037b7dea7ed.zip”.
  2. Unzip the downloaded archive file by double-clicking on it. (My Safari browser automatically unzipped the archive file after downloading.)
  3. Launch the Terminal app and run these commands:
    # Rename the unzipped folder to a nicer name, "patch-edid"
    mv ~/Downloads/7435890-00ff3ead17ae77d2f1c376e90831c037b7dea7ed ~/Downloads/patch-edid

    # Change directory to the "patch-edid" folder
    cd ~/Downloads/patch-edid

    # Ruby should be pre-installed; double-check by getting version info
    ruby -v

    # Execute the script
    ruby patch-edid.rb
    • The script outputted the following on my Mac:
      Found display 'DELL U2410': vendor ID=4268 (0x10ac), product ID=61462 (0xf016)
      Raw EDID data:
      00ffffffffffff0010ac16f04c5055310914010380342078ea1ec5ae4f34b1260e ...
      Setting color support to RGB 4:4:4 only
      Number of extension blocks: 1
      removing extension block

      Recalculated checksum: 0x38

      new EDID:
      00FFFFFFFFFFFF0010AC16F04C5055310914010380342078E21EC5AE4F34B1260E ...
      Output file: /Users/chanh/Downloads/patch-edid/DisplayVendorID-10ac/DisplayProductID-f016
    • Take note of the output file, “/DisplayVendorID-10ac/DisplayProductID-f016”. We will need to put the ProductID file with its VendorID parent folder under the EDID overrides folder like so: “/System/Library/Displays/Contents/Resources/Overrides/DisplayVendorID-10ac/DisplayProductID-f016”.
    • On my Mac, the “DisplayProductID-f016” file did not exist in the system “Overrides” folder. However, the “DisplayVendorID-10ac” folder did already exist there.
  4. Reboot into the macOS Recovery Mode. When the Mac starts up, hold down “Command-R” (hold down both the “Command ⌘” and “R” keys) and release when you see the Apple logo.
    • Tip: An easier alternative is to hold the “Option/Alt” key on boot to launch the Startup Manager. Then just click and release “Command-R” keys to launch into the recovery mode.

  5. Once in recovery mode (you will see “macOS Utilities” in the top menu bar), click on the “Utilities” menu and select “Terminal” to launch the Terminal application.
    • On my Mac, the main “Macintosh HD” drive is automatically mounted. If it isn’t on your system, launch the “Disk Utility” first (before the “Terminal”), select the “Macintosh HD” disk (or whatever you named it), and click the “Mount” button. Quit the “Disk Utility” when done in order to launch the Terminal application.
  6. Run these commands in the Terminal:
    # Change directory to your "patch-edid" directory
    # Note: Change the "username" string below to your actual username
    cd /Volumes/Macintosh\ HD/Users/username/Downloads/patch-edid/

    # Copy your override subfolder+file into the EDID overrides system directory
    # Note: Change the "DisplayVendorID-XXXX" to your actual DisplayVendorID
    #       Do not include ending forward-slash at end of "DisplayVendorID-XXXX"
    cp -R DisplayVendorID-XXXX /Volumes/Macintosh\ HD/System/Library/Displays/Contents/Resources/Overrides/
  7. Quit the “macOS Utilities” to reboot.

After reboot, the text on the Dell monitor is no longer blurry and pixelated. The text looks sharper and the lines are smoother. (Unfortunately, the photo to the right does not show the blurry/pixelated text very well.) When I check the monitor’s “Input Color Format”, it now says “RGB”. Success.

13 Comments

  1. Andrei

    Does not help in Catalina (10.15.2), maybe somebody knows any new fix?

    • Chanh

      Thanks for the update about it not working under macOS 10.15 Catalina, Andrei. I only did it on macOS 10.14 Mojave with the Dell U2410 monitor. (On a side note, I have an older Dell 2407WFPb monitor which puts itself into “Mac mode” when connected to a Mac. So, Dell used to support Macs correctly.)

      • M1kz

        Thanks for the guide – I followed it verbatim today and it works fine in MacOS Catalina 10.15.3 with a Dell U2410.

  2. Kz

    thanks so much. It fixed my problem. There needs to be an easier way for Macs to select the color mode. MacBook Pro (Retina, 15-inch, Late 2013) 10.13.6 (17G8030)

  3. gpi

    Unfortunately, this didn’t solve my problem. Any other idea?
    MacBook Pro Retina 2019
    Dell S2719DC

    • Chanh

      Not sure. I found this page, 2018 MacBook Pro blurry displayport output, which suggests that the issue is related to using the USB-C to DisplayPort cable. The workaround was to use a USB-C to HDMI cable instead.

      • G

        I have followed your instructions above. I did force the monitor to have RGB connection. I used patch-edid method that you have described. I am using USB-C cable for connecting the display to the laptop. I also tried HDMI to USB-C cable… same blurry result.

        Idea?

        • Chanh

          Thanks for letting us know the results. Unfortunately, I don’t have any other idea.

  4. Elli

    Hello! I’m having trouble with this part on #6:
    When I typed in this command on the terminal, I get “command not found.”
    I’m not really sure why.

    -R DisplayVendorID-XXXX /Volumes/Macintosh\ HD/System/Library/Displays/Contents/Resources/Overrides/

    ^I literally copied the same code you provided and replaced the “XXXX” with “10ac”

    Any ideas? Thanks!

    • Chanh

      Hi, two guesses:

      • Command not found might be because the copy command “cp” is missing from the beginning. It’s supposed to be “cp -R”, not just “-R”.
      • Try running the list command “ls” to show the contents of that directory first to double-check that the “DisplayVendorID-10ac” subfolder actually exists.
  5. Jeerral

    Didn’t work for me 🙁

    Macbook pro 2017
    Benq EX3203R

    I’ve nearly tried all the solutions on the internet, none of it works

  6. Gurkirat Singh

    Thanks. Worked for my MBP 2015 with Catalina and Lenovo monitor…

  7. Jean-Yves

    Thanks a lot for this tutorial : I just bought a Mac Mini 2020,
    running Catalina of course, and this works like a charm for
    a Dell U2410.

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