How to solve Mac error -9923 when scanning over a network

Mac error -9923 can occur when scanning over a network, under some conditions. If it does, you might get a message saying “An error occurred when communicating with the scanner.” The result: you can’t scan.

The problem seems to pop up out of nowhere. And printing will continue to work. It’s only scanning that’s an issue. Weird.

If you do a Google search for this issue you will find many totally unhelpful tech “support” responses from HP and Epson (Canon is better). They tell you to uninstall drivers, reinstall drivers, turn the printer/scanner on, turn the printer/scanner off, restart the router, restart your Mac, restart the coffee pot. Total waste of time.

The real answer is in the network settings. You have a choice: adjust the printer’s network settings (harder, but it solves it for the whole office), or adjust your Mac’s settings (super easy, but it only solves the problem for you).

Solving the problem by adjusting the printer’s network settings amounts to turning OFF IPv6 on the printer. This is done various ways, depending on the printer. With some printers, you’ll see a panel on the front, and you’ll go to the Settings, and then Network (or maybe LAN settings), and eventually you will find a place to turn IPv6 off. With other printers, you’ll type the printer’s IP address into a browser, and that will give you control over the printer’s settings. Some printers come with their own Mac app, which you can use to adjust settings. Either way, it all comes down to one thing: you want to turn OFF IPv6 on your printer.

The easier way: fix it at the Mac end. Go to Apple menu / System Preferences / Network, then click the Advanced button.

Network preference pane
Network preference pane. Click “Advanced…” button.

After you click Advanced, click TCP/IP (at the top). Then change IPv6 to “Automatically.” Then click OK, then click Apply. Then close the System Preferences window.

Configure IPv6 Automatically
Setting IPv6 “Automatically” in Network preference pane

If IPv6 already said “Automatically” try changing it to Link-local, then clicking OK, then clicking Apply. Then go back in and change IPv6 to “Automatically” again.

If I were you, I’d try changing my Mac’s Network settings first. It’s easy, and easily undone. If it works, great– you’re done. If it doesn’t work, put things back the way they were, and then tackle the problem from the scanner/printer’s end, by changing the printer to disable IPv6.

As you can see, both methods try to match up the Mac’s network settings with the printer’s. In the first case, we change the printer’s settings so it matches the Mac’s. In the second case (the one I’m recommending), we’re changing the Mac’s setting to match the printer’s. Regardless of the method, the proof is in the scanning: if, after changing the Mac’s settings, you can scan, voilá! If you can’t scan, change the printer’s settings (in the printer itself). That should do it.

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46 thoughts on “How to solve Mac error -9923 when scanning over a network

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  1. Thanks so much for this! Fixed it!

    I also agree with your points about the official tech support suggestions – it’s always on the lines of uninstall drivers, reinstall, turn off, turn on, put your right foot in, put your right foot out, turn around and shake it all about, reboot the router, reboot your laptop, reboot your life, etc etc etc. A lot of work and rarely works.

  2. I was using Express VPN and I tried disconnecting from it and it reset it without doing anything else and then I turned VPN back on and it seems to have fixed it. Lets see how long that lasts.

  3. Thanks! Works perfectly. I just bought a new Canon printer and the scanner wouldn’t work. It was driving me nuts. If you have time, could you please explain why changing this setting will allow the printer to work?

    1. Basically, the “old” style of internet address was IPv4. Addresses look like this: abc.def.ghi.jkl

      That is, the address is in four parts. If you look in your network settings you will see something like this: maybe 192.168.1.x or 10.0.1.x.

      This is all very good if the printer has an address in the same family. And it would, except… somewhere along the way, a new standard for IP addresses (Internet Protocol addresses) was developed, because we (the world) were going to run out of unique IP addresses someday if the addresses were in the IPv4 format. You can see how that could happen.

      So… “they” came up with IPv6, because the addresses are way longer than IPv4 addresses, and therefore there are many times more unique addresses for us to use. Great stuff, except it came out of a committee (which is fine) but there were details that weren’t quite agreed upon, so every implementation of IPv6 networking could potentially be a little bit different, depending on the company that made the networking equipment or card in the device. (For that reason, it is often better to keep using IPv4, at least for the time being.) A lot of devices (including Macs) let you turn on both kinds of networking, and somehow the “right” kind of networking is grabbed and everything is great. Generally, what was grabbed was IPv4.

      For some reason, either scanning over a network is an IPv6 thing only, or your scanner insists on IPv6, so we just have to get our Macs to obtain an IPv6 address, so we can talk to it. It would work either way: tell the scanner to speak IPv4, or tell the Mac to speak IPv6.

      I hope that explains it.

  4. Hi Christian-

    This worked briefly (turning off IPv6 at the printer, Canon TS9120). Now it’s back to the 9923 error after I changed NOTHING. I’m about to throw my printer thru a wall. Any other suggestions? FWIW…I also tried to change the IPv6 address manually at the printer. No luck there either.

  5. Thank you Mr. Boyce, it works for me as well.

    I tried to disable the IPv6 from my printer end (HP DeskJet Ink Advantage 5275). It did’t work. Then, I tried your second solution, which is change the IPv6 from Automatically to Link-local Only to returned it back.

    By the way, I found your site as the first suggestion by Google when I searched for “scanner error 9923”. GREAT 🙂

    Have a good day,
    best regards.

  6. You have made my day. With your instructions I was able to switch off the IPv6 on my Cannon Printer. I tried the Mac solution first but it did not work for me. I’m a very happy 79 year old lady!

  7. Hello. I have HPDeskJet 3630 All-in-One. Everything worked perfectly until we moved into a new apt and I had to connect my HP through network. After 3.5hours when it finally worked, my printer is OK, but scanner function is not working. I tried your advice, but no result. Can you please help what else I can try ? Thank you.

  8. I changed settings in Network – TCP/IP from Automatically to Manually and then back to Automatically, and then from Automatically to Link-local only and back to Automatically …

  9. well, I went to printer settings via browser but cannot find where to disable IPv6 – I can only put there Manual IP address …but at least I found there webscan and enabled it so in case of emergency I will use it …anyway, thanks for helping me out and if you can advise me, hot to turn off that IPv6, I will be glad …thank you

    1. You’re close. I don’t know what the settings look like for the printer, but you are in the right place. Once you get to the settings in the browser take a screenshot and send it to me– macman at christianboyce dot com. I’ll have a look.

  10. I tried this many times, both on my Mac and on the printer (Brother LCP-L2550DW) and the printer still doesn’t recognize the computer. 🙁

    1. Interesting the way you phrased it: “the printer still doesn’t recognize the computer.” It makes it sound as if you are trying to scan by pressing buttons on the printer and sending it to the computer. I would do it another way. First, be sure you can print from the computer. That’s a quick networking test. Then, go to the Mac App Store and download Brother iPrint&Scan. Here is the link to the app on the App Store: I have a Brother Brother MFC-J430W and this software made it work. The key is, you control the scan from the Mac, not from the printer. Put your picture on the glass, start the iPrint&Scan app, click Scan, and you’re done. If you really want to scan by pushing buttons on the scanner, you’ll have to download “iPrint&Scan Push Scan Tool” (you’ll be asked to do that after installing the iPrint&Scan app). I didn’t install that because I was happy scanning from the Mac, and I didn’t want to mess with something that was working!

  11. Hi,

    I am trying to do this but for some reason the option is unclickable on my laptop. I cannot change any of the advanced settings. Any ideas?

    1. Fantastic. Check out the lectures I’m giving online– see, look for “Lectures,” watch a video or two! Sign up for the mailing list to find out about what’s coming up next. FYI.

  12. I tried everything including restarting the coffee pot, but nothing worked and the problem has continued off and on for 1-2 years. What finally may have worked was unplugging and moving the router off the floor to a higher position with a clearer and less-wall-obstructed line of sight to my devices AND moving the printer to be closer to the router. So far, so good.

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