Mac OS No longer has a serial number and shows "Serial Number (system): Not Available" in system profiler.


  1. I had a botched filesystem runnig mac os Catalina 10.5.7, and so i decided to do a clean install, and then do an internet recovery. To be sure my ssd was totally clean including the efi partition, i zero'ed the drive with dd. Then, booted to internet recovery, which oddly booted up to Big Sur recovery even though i never upgraded to Big Sur. I decided to install Big Sur anyway via internet recovery, and after the install, i noticed that in "About this mac" as well as through a terminal command, that my serial number was labeled as "unavailable", and is no longer recognized in the MLB of the "Mail logic board."
  2. Furthermore, i noticed that my icloud automatically signed my mac out from my icloud interface in the settings panel on my iphone. I never signed myself out before erasing.


One more strange quirk is that apparantly, this somehow also deactivated all of apples DRM (digital rights management) for any of the apps that i had purchased. I concluded this, because after the clean install from internet recovery, I DID NOT SIGN INTO ICLOUD. Then, instead of importing my files with migration utility, i simply dragged and dropped my digitally purchased app store apps from my time-machine backup, onto my clean install. After removing time machine drive, i opened the apps, and low and behold, all of them worked perfectly without asking me to sign into icloud, or log into the app store. How is this possible?


  1. Supposedly, once a certified apple technician burns a serial number into your logic board, it is impossible to remove unless you have specialized software that contacts apples servers with a registered signature and encryption key, and waits for apples servers to send authorization to write or remove the serial number from the logic board. Assuming that apples technology is impenetrable, then you would have to assume that someone stole apples special software and one of their keys, and used it on my logic board remotely to deserialize my mlb.

  2. The other possibility, is that apples hardware and logic boards are flawed, and they can erase their oen serial numbers. other than that, im out of ideas.


  1. Can someone explain how i lost my serial number, and explain the weird quirks (missing drm, unauthorized deregistering my mac from icloud) that are happening as a consequnce?

  2. Then, can someone please tell me how I can get my serial number burned back into the mlb so that i can use imessage on my mac again?

  3. I found a website with some software called BlankBoard Serialzer at https://www.macintoshrepository.org/26584-blank-board-serializer?ns=1 Could anyone tell me if this sofware is safe to use and if I should use it to re-burn my serial number into my mac?

Thanks for any help! Check screenshots below!

About this mac, serial number unavailable Macos big sur serial number unavailable

  • 2
    Not sure why this was downvoted. I never knew this was possible, but you learn something new every day! Having a quick look on the internet, it appears that it is only possible if the Apple authorised repairers failed to write the Serial Number to the replacement logic board? But I've also heard some 2013 MBP users have had their system bricked since updating to Big Sur, so maybe search for advice about that? I think Apple did release a patch update for those affected models. Hope this helps
    – AVelj
    Commented Dec 18, 2020 at 10:23
  • 4
    It's always a mystery why people downvote. OTOH your question might get received better if it would have more focus on the problem you want to solve and less detail about any assumptions and guesses you might have. This would make it easier to read and understand the question (long texts usually are skipped quickly)
    – nohillside
    Commented Dec 24, 2020 at 10:31
  • Also, what kind of research and problem solving have you already done on this? apple.stackexchange.com/questions/379699/… seems to be related, as are some other questions about missing serial numbers.
    – nohillside
    Commented Dec 24, 2020 at 10:32
  • Try booting into Apple Hardware Test (press "d" on startup)? Try booting to the version of macOS your machine comes with and see if that version of macOS will recognize your serial number?
    – Joy Jin
    Commented Dec 24, 2020 at 11:13
  • 3
    I'm just going to echo @nohillside here—this is a very interesting question, but it would be much better if it was edited to be much shorter. This is a bit of an art, as if you include too little background, the question will lack necessary information... I generally just follow the principle that a question isn't just for me, but also for future users, which means choosing the information that is likely to be broadly applicable. Commented Dec 24, 2020 at 15:02

3 Answers 3


Question 1a:

We don't know all the steps you have taken (and you may not remember all of them very clearly) in your reinstall. So hard to say why. The most common causes are some hardware change, but you say this does not apply in your case. Of the steps you mention using dd is the only unusual step - I would have used Disk Utility in Internet Recovery.

Question 1b:

You have already discovered that some Apple services require a valid serial number. iMessage and various DRM are tied to your serial number and UUID as well as Apple ID. As an aside, loading a valid serial number is a tricky and important step in getting a Hackintosh to run iMessage.

Question 2:

The best solution is to take the MBP to an Apple Store where they may well fix your problem for free - just say it happened during a macOS upgrade (which is true in your case).

Question 3:

The Blank Board Serializer is an Apple tool and can be used to fix your Serial Number. It is important to find the version which is compatible with your MBP - I can't help you there.

Have a read of these three links which describe the process which must be following very carefully - the first one has lots of comments from those who have succeeded (or not) using this method.

Roger Sen

What causes Mac to lose its serial number

How to fix missing serial number


  • However you fix this (either via Apple or yourself) make very sure you enter the correct serial number belonging to your Mac. You only get one chance to get it right.
  • If you do it yourself, be prepared that you might get it wrong and brick your MBP.

Additional warning:

  • Read @DanRan's own solution and heed the warnings about the need to unregister the Mac and unauthorise from any services which have been used with the incorrect or blank serial number.

The reasoning why this occurs is unknown to the general public. But the issue appears to be related to OS changes and unofficial hardware changes. As for a fix, if your Mac is still under warranty, take it to the Apple Store so they can correct the issue.


For those who experience this problem, I partly solved the issue (which created a new issue) by doing the following:

THE SOLUTION: I took my mac to the Apple store, and showed them the missing serial number. The Apple Technician connected my mac to Apples servers and reflashed my logic board with the correct serial number right in front of my eyes all for the price of $0.00 without apple care or a warranty for my mac. So, the Apple Stores do have the proper software, means, and ability to reflash your serial number into your MBL if this issue happens to you.

THINGS TO CHECK BEFORE TAKING IT TO THE APPLE STORE: After I had the Apple store reflash my macbook pro with the original serial number, I encountered a new problem, that may not have occured if I took care of this issue BEFORE REFLASHING THE SERIAL NUMBER AT THE APPLE STORE.

The NEW Probem: Reflashing the Macbook pro with the serial number (possibly) created a permanant issue in icloud. Now, when using the icloud web interface, my iphone, or my mac, i CANNOT REMOVE the Old macbook pro with the "UKNOWN" Serial number. This means, that when trying to reformat my newly flashed mac, and start from scratch, icloud somehow thinks my macbook is permanently logged in and will not de-register "Macbook Pro: Unknown Serial number" from icloud using any means or methodology. I have no idea if this issue existed before reflashing my mac serial number, but i believe it didnt. Therefore I suspect the issue comes from the fact that iCloud is detecting two of the exact same hardware and logic board configurations with different serial numbers.

IF YOU ARE TAKING IN YOUR DESERIALIZED MAC to the APPLE STORE TO REFLASH THE SERIAL I would strongly suggest to do the following before hand:

  1. Unregister your mac with the "UNKNOWN" serial number from all off apple services including imessage, icloud, app store, itunes store, icloud, and any other apple service you can possibly think of. THEN Verify that your deserelized macbook pro DOES NOT SHOW UP in icloud from your phone, or from your icloud panel on another mac. If It DOES SHOW up after deregistering it form icloud, then you have the same problem, and should show this to the apple technician before reflashing the serial number onto your mac.
  2. Be sure to de-authorize your mac from the iTunes store, and any other apple services. Note that de-authorized and unregistering are two different things. Do both, especially with itunes.

If you have the same issue, and these steps work for you please leave a comment so I can update the solution. Hopefully this helps anyone else out there.

  • Ouch! Very good point about the need to unregister and de-authorise beforehand.
    – Gilby
    Commented Mar 23, 2021 at 21:32
  • @Gilby, Thanks! I just wish I knew this before I re-registered. Now its going to be a long elevated process of being on the phone with Apple Support. Hopefully the engineers will take a look at it for me.
    – DanRan
    Commented Mar 23, 2021 at 22:19
  • @Gilby, I did about 2 hours on the phone with apple support and then they elevated it to engineering. I awaited a call from them, but my autoblocker unknowningly blocked their calls. Instead of repeating the process, I did nothing. After about 3 months of waiting, the problem resolved itself. I'm assuming apple found the glitch and corrected it on their own. What was your outcome to this?
    – DanRan
    Commented Aug 17, 2021 at 2:16
  • Very glad it has turned out right in the end. My only direct experience is that I had a mainboard replacement in a MacBook (Bluetooth stopped working) and the local Apple Authorised Repairer forgot to put the old serial number in the the new board. I noticed straight away and took it back the next day and they fixed it.
    – Gilby
    Commented Aug 17, 2021 at 6:23

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .