Force RGB mode in Mac OS X to fix the picture quality of an external monitor

I recently bought a MacBook Pro (with ‘Retina’ screen), but when I hooked it up to my Dell U2410 monitor via HDMI cable I was shocked by the poor picture quality. The contrast was all wrong and text was misshapen. No amount of calibration in the monitor or software would fix it.

Short answer: OS X thinks my monitor is a TV, and is using the YCbCr colour space rather than RGB. I had to override an EDID setting to force the RGB colour space, and it is now working correctly.

Long answer: I haven’t owned a Mac for a while and had forgotten how difficult much of the “Apple community” can be when it comes to anything that can’t be adjusted in System Preferences. Googling for problems with external monitors on MacBooks found dozens of threads on official and unofficial Apple forums, all full of people with the same problem. The most common response was to blame the monitor, despite assurances from the stricken users that the monitor worked beautifully in Linux and Windows, even on the same machine under Boot Camp.

“You just haven’t calibrated it!”, “You are just too used to Retina now!”, “You just need to buy a Thunderbolt display!” Apple people also like to solve problems by throwing more money at it. (I realise that owning a Mac makes me an Apple person, too. Hypocritical self-loather?)

My lucky break was reading that the current colour space was “YCbCr” when I was browsing the monitor’s settings menu. I was sure that it was using RGB when hooked up to my PC, so I started searching instead for forcing RGB mode in OS X. It didn’t appear to be available out-of-the-box, but I have had some experience in overriding EDID settings for similar purposes so I searched instead for that.

I found this thread on the forums. Mr Schwarz, thanks very much. Your thread and script was incredibly helpful and informative. It was written to fix problems connecting an external monitor via DisplayPort, but it fixed my HDMI issue just the same. I’ve summarised the required steps below.

My last word is to wonder what Apple is playing at. It seems that this problem has been reported by a lot of people for a long time, and I expect it would require a fairly simple software update. Do they just not care about those using third-party components, or are they actively attempting to force people on to Thunderbolt displays?

How to force RGB in Mac OS X

These steps have been updated for Mac OS version 10.11, “El Capitan”. See below for differences for previous versions of the system.

  1. Download the patch-edid.rb script from the forums thread above, or download Andrew Daugherity’s improved patch-edid.rb script from his github page. Put the script in your home directory.
  2. Disable “rootless” mode, you can follow these instructions: How to modify System Integrity Protection in El Capitan.
  3. Reboot.
  4. Connect only the external monitor(s) in question, if you can (I closed my MacBook lid, for example). The script will make override files for any connected monitor.
  5. Type “ruby patch-edid.rb” in Terminal.
  6. A new folder will be created in your home directory. Move it into the “/System/Library/Displays/Contents/Resources/Overrides” folder. You may have to create the Resources and Overrides folders. If Finder tells you that you are overwriting an existing folder, consider backing it up first.
  7. Restart your computer. The picture quality should be fixed from this point.
  8. Re-enable “rootless” mode, the instructions are available on the same guide: How to modify System Integrity Protection in El Capitan.
  9. Reboot. Enjoy your monitor.

To undo the changes, either delete the folder you had copied to the Overrides folder (if it didn’t already exist) or replace it with the folder you had backed up. You will need to re-enable rootless mode to do this.

Earlier versions of Mac OS X

The process is a little more straightforward. There are two differences to the steps above:

  1. You do not need to disable/re-enable rootless mode and perform the subsequent reboots.
  2. The overrides folder location is “/System/Library/Displays/Overrides”.


I no longer own a Macbook Pro, but if you’re having trouble with any of these steps, please have a look through the comments below (and note that there are multiple pages). Many questions have been answered with helpful tips from others.

Update, 8 Feb 2016: A comment from nos1609 below, warns about a bootloop that can occur when running other patches (like the pixel-clock patch) simultaneously, and how to get around it.

Update, 23 Nov 2015: According to Peter’s post, you don’t need to disable SIP if you use recovery mode. If others have similar success with this method I’ll update the process.

Update, 3 Oct 2015: I have amended this post to target El Capitan. I have taken the steps from bigmcguire’s process, posted in the comments. Although some are still having issues, it appears to be working for people. Thanks!

Update, 29 May 2015: Mac OS 10.11 El Capitan does things a little differently. You must first disable the new ‘rootless’ mode and then use a different overrides folder: /System/Library/Displays/Contents/Resources/Overrides. Rootless can then be re-enabled if desired, as confirmed by nos1609 in the comments below. El Capitan is still in beta, I’ll update this post if the issue is still apparent afterwards.

Update, 26 May 2014: If you have had trouble with limited resolutions being available after the fix, check out Ibrahim’s comments here.

Update, 28 Nov 2013: If the process appears to work but doesn’t seem to make a difference, consider Tom’s comments below. Depending on your monitor an extra tweak may be required.

Update, 13 Nov 2013: Andrew comments below that he has modified the script to add some useful new features, and provides a link to his GitHub for those wishing to use it instead.

Update, 27 Oct 2013: If you’ve applied this fix before, the OS X Mavericks update will overwrite it. I’ve successfully re-applied the fix by following exactly the same steps, and other commenters below have done so, too.

851 thoughts on “Force RGB mode in Mac OS X to fix the picture quality of an external monitor

  1. I upgraded to Sierra before remembering I had to do this hack to get my old Mac mini to work well with an external display. So glad this page still exists!

    Here are the steps I had to follow, since I don’t have a Recovery Partition on this computer, and Internet Recovery uses a very old version of OS X that doesn’t have the csrutil utility.
    1. Download Sierra installer again.
    2. Follow the steps on Apple’s site to make a bootable USB drive.
    3. Reboot and hold down Option and then select the USB drive.
    4. Wait forever for it to boot.
    5. Use the Terminal to run csrutil disable.
    6. Follow the steps above.
    7. Rejoice in my white windows actually being white instead of gray!!!!
    8. Try to remember to re-enable SIP.

  2. I’m running Sierra (MacBookPro) and trying to use this solution for my Asus monitor. I’ve downloaded and unzipped the .rb file and placed it in my home directory, but when I run the ruby patch-edid.rb in Terminal, nothing appears to happen. A new Terminal line appears, and no new folder is created in my home directory. Does anyone know what I might be doing incorrectly? Thanks!

  3. Hi – I sent these instructions to someone and they had a little trouble. For step 6, I’d suggest clarifying that they may have to create the Resources and Overrides folders. There is an Overrides directory under a slightly different path that seems to be confusing. Path has to be exact and I think is overlooked sometimes due to the presence of a similar path.

    Also, for being able to close your laptop without it turning off, (as suggested in step 4), there is a free package called SetResX by Paul Griffin (thanks!) that can help accomplish this. Sometimes hosted on some spammy websites though, so be careful.

    These steps work though.

  4. Works for me.. awesome!
    I had my monitor connected with serial port initially. Switched to HDMI but the text looked all blurry.
    This solution works for me on Mac OS Sierra. Thanks

  5. What I got. Maybe help somebody .
    Mac mini 2012,Osx 10.10.5 // display PIONEER KURO PRO 110FD.
    I can options on TV ,control input signal . you can see from manual \Pioneer KURO .

    Problem not in MAC or TV ( monitor)
    problem in cable.
    HDMI send YCbCr colour space . Check different HDMI cable like 1.2 1.4 2.0 My all HDMI pick from Mac YCbCr colour space .
    and now DP (thanderbolt) to HDMI :
    My old chip from Ebay DP to HDMI send RGB signal.
    I got brand new DP to HDMI from eBay and this cable send on the same system YCbCr colour space .
    I have control option on my Pioneer KURO and can see what signal arrived in my tv.
    From KURO manual :
    • If you select “Auto”, an attempt will be made to identify the type of digital video signals when digital video signals are received.
    This is option for input signal:

    Auto (default) Automatically identifies input digital video signals/////////////////////////////any cable you never know
    Color-1 Digital Component Video signals (4:2:2) locked/////////////////////////////////////HDMI-HDMI, new DP-HDMI
    Color-2 Digital Component Video signals (4:4:4)locked///////////////////////////////////////HDMI-HDMI, new DP-HDMI
    Color-3 Digital RGB signals (16 to 235) locked////////////////////////////////////////Old DP to HDMI
    Color-4 Digital RGB signals (0 to 255) locked///////////////////////////////////// Old DP to HDMI cable
    4K*2K HD TV To HDMI Adapter Cable 6ft 1.8m Mini DisplayPort DP Thunderbolt Cord
    This is DP -HDMI cable new one send YCbCr colour space:


  6. This resolved my monitor issue as well. Also, I just upgraded to macOS Sierra, and it still works. I have an Acer K272HUL, which is a good monitor, but I could not get rid of the jaggy text. This solution worked and the difference is like night and day. The text looks absolutely great. I also noticed in my System Preferences -> Displays – Refresh Rate is not 60 Hz as before. It is now 59.88 Hz. Thanks again to everyone who contributed to finding and posting the solution!

  7. MBP Mid-2012 non-retina, hooked up with Dell U2414H. GeForce 650M. Closed lid, therefore running on the 650M and not the built in graphics.

    Im not sure if my screen shows weird colours. Would it be easy to notice? Should text look weird too, you say. My screen is found as a TV by OS X, and when I had El Capitanthius “trick” removed the shown as aTV-problem, but I cant say if the colours, graphics etc looks different.

    Now using Sierra (not preview), it seems like the settings have been restored and my screen is found as A TV again. Did or did it not work to do this trick in Sierra, and what is the benefit if the screen shows, from what I cat tell, the right colours?

    How to tell if things are OK or not, and could it be fixed even in Sierra?

  8. I am trying this with a BenQ GW2765, connected to a 2012 Mac mini via HDMI. The script seems to run OK, and I get the new display profile, bit it makes no difference. Text is still fuzzy, and I can’t get the max resolution.

  9. The resolution seems to work fine, but it the monitor (ASUS PA279Q) still shows up as Television in my Display Systems Report (Apple Menu). Would this be considered a full use of the Adobe aRGB on my monitor?

  10. I’ve followed the steps to step 5. When I type the “ruby patch-edid.rb” in terminal it says command can’t be found or something like that. I’m not a programmer or anything of the sort. Is there something I’m doing wrong?

  11. I got a CX271 EIZO monitor, and when using it in windows bootcamp displays pures blacks and pure whites (Full dynamic range 0-255 enabled in nvidia driver) while in macosX blacks and white are faded.
    Is there a solution to fix that ?
    I tried to force recognition of my screen and nothing append (just a profile created in my display panel in macosx preferences). Blacks and white are always dead.

  12. This worked on a MacBook Air 13 ince Early 2014 that was having strange text issues on a Dell P2815Q. Thanks a bunch! Saved me some moolah

  13. So this used to work PERFECTLY for me, but now since updating to the latest version of OS X (10.11.6) it seems to not be working fully. System information doesn’t show it as being a TV anymore:

    But in the display preference pane it’s still only giving me TV resolution:

    I even recently bought a Mini Display Port to Mini Display Port cable to try and fix the problem.

    This is so absurdly frustrating, and I don’t know who’s to blame – Apple or Dell – but I am ready to pull my hair out (and sell this monitor for one that works reliably).

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