The operation could not be completed (CKErrorDomain error 15)

Info says CKErrorDomain 15.

What does this error mean and how do I fix it?

This is an error with Apple’s servers, not a sync problem. It should (hopefully) be temporary but it’s nothing we control.

  • Do you actually need to use a remote sync option?
    • If so, I’d suggest you look for an alternative.

Which ones should I evaluate.

Would drop box be best


If you must sync, I recommend you first setup and use Bonjour. Quick and reliable. If third-party internet syncing needed, you can add in another. Dropbox works well for me.

Failure and unreliability of Apple’s sync services for some people, including this specific error name, has been discussed (and advice offered) ad nauseam on this forum.

I use WebDAV in my Synology NAS in a double-encrypted way: the “partition” where the sync database is, is encrypted by Synology, and the sync database itself is encrypted by DT/DTTG.

This is not true, this error can also be caused by malicious requests to the server. In order to understand what is causing the error on server-side, you’d need to check context of the request. It might be that large data sets are queried or something else might have requested wrong.

I’m currently evaluating DEVONthink as an alternative to Evernote. It’s quite important for me that syncing documents via iCloud works without issues. If the statement here is, iCloud is unreliable (which is not the case), then it’s definitely a blocker for me.

@BLUEFROG Could you please elaborate more specifically on the issues with iCloud to understand if DEVONthink is a valid replacement for Evernote (for me)? Thank you!

If iCloud is not unreliable, then it must be reliable. Which seems to be contradicted by the numerous web articles on “How to unstuck iCloud sync” etc.

iCloud is unreliable for some. Other users seem to be happy with it. Personally, I sometimes experience long delays for Cloud Drive sync and Photos. And Apple’s track record re networking in general is bad.

For DT sync, I rely on my own NAS with WebDAV which always works without a flaw. Others suggest Dropbox or Bonjour (if you don’t really need on-the road sync because other people are simultaneously working with your databases).


I’m years, but years, with WebDAV in my Synology (in fact, two because I replace one some time ago for a powerful new one) without any sync issue, and if I had got one, have been after Synology updated itself and then I have to manually mount the sync partition as it is encrypted.


iCloud is unreliable (which is not the case), then it’s definitely a blocker for me.

iCloud, has been very unreliable for many people, including other developers, in the past year or so. This is especially true for CloudKit. As @chrillek mentioned, there are numerous posts, queries, reports, etc. on the topic of its unreliability. And Apple continues to make changes under-the-hood that can lead to unexpected behavior for the user. See Howard Oakley’s recent post…

It’s quite important for me that syncing documents via iCloud works without issues.

  • Why? Do you actually need a remote sync option?
  • Have you actually tried using an iCloud sync in DEVONthink?
1 Like

Yes, I need the remote sync option on the go.

Yes, I’ve set-up CloudKit sync and it works quite well for me. But I’m annoyed and distracted by the log window popping up at least every hour and logging this message. Same on the iPhone with DEVONthink To Go. If this error is temporarily and can be ignored, why can’t it be catched in the apps internally?

That has already been discussed. The error is raised by the Apple infrastructure, and you should talk to them to inquire whether it is temporary or not. I guess “catching” an error that is labelled “irrecoverable” by Apple is not an option.

Sure, if it caused by Apple infrastructure and irrecoverable, the app should still try to handle it with more resilience. Queuing the same operation for another time/with delay or re-trying the operation for a certain number of times.

And if all of it fails: I’m the user of the app and not the vendor. As far as I’ve understood the intermittent error can be reproduced by the vendor and could contact Apple with the exact payload of the API operation (which is hidden from me). No?

It hasn’t been unreliable for me and my family using apps with Cloud Kit (Notes, Reminders, Photos, Notability, etc.) or Cloud Drive to sync data on multiple connected machines, mobile phones and tablets.

I know that Apple has historically not the greatest track of record in regards to networking/infrastructure issues, but after all, it seems they have worked out a quite reliable ecosystem nowadays. Hence I’ve subscribed to the 2 TB iCloud storage and looking for apps, that make use of it.

There are hugely different opinions on that. It all boils down to this: If you think that Apple’s services are good enough for you, go with it. But you shouldn’t hold others responsible if said services fail you. This forum is full of posts where people are encountering the same CKErrorDomain errors over and over again, and all these errors are Apple’s responsibility.

There are other, definitely more reliable sync options. If you decide against them, that’s your choice.

And frankly, the whole idea of having a cloud service “manage” my personal data in that it removes them at leisure from my disk is hilarious.

That does not mean that you have lost your data. Whatever thing could not be synchronized in that moment, will be later.

Let me be a little unpolite: that is a fantasy of today and tomorrow. There was an era when Apple took care of that and listened to customers. That ended some years ago and Apple does not mind how many bugs or issues their software have, they are only worried for their investors accounts and how much money they make for them. As developer myself, in private betas of Big Sur and Monterey, I reported about 20 bugs related to PDF issues. No answer and, of course, no bugfixing. And this behavior is typical of Apple. I had a serious iCloud issue, more than one month without iCloud (any service), tired of not getting a solution from their “Geniuses”, online support, sending them what was happening with low level traces from their own servers, etc, finally I moved some strings and got an email and I complained to that email… Two days after that, I got a contact that resolved the issue in two hours… starting one of their own internal credential and certification server, what was down. Any user that had that specific server assigned for that purpose couldn’t connect to their iCloud in about one month. Nobody noticed it, nobody took care of it until I had to send a profoundly serious email that, luckily, was attended.

(And, btw, that is the reason I’m quitting from Apple. My iPads are off, my main Mac mini of 2500 euros is off, replaced by a 800 euros NUC that does the same faster and with less issues, and I couldn’t return my iPhone 15 Pro Max because I gave another phone and had lost the price of that one if I rerurned it).


I don’t. I hold the vendor responsible to check if there is something wrong with their API usage. This might be limitations in size, number of affected objects, etc. This is nothing I can handle on my own with Apple.

Also: How about all other apps? I’ve never seen this error popping up before in ANY of the apps using CloudKit. This being said: If vendors of other apps are simply hiding the error from the user, this should reveal issues in syncing in general. But I haven’t had any issues so far. So what now? Should I live with the error popping up continuously the next years?

DEVONthink has long history of developing software in the Apple ecosystem and I had naively assumed they are quite well associated with them. If this is assumption is not correct, I’ll retract of considering DEVONthink as a reliable alternative to Evernote. Easy for me.

The error recurs as our sync engine retries on its own periodically instead of putting the burden on the user to reinitiate a sync manually. The log messages are the result of that activity, letting you know it’s still trying. I’d say that’s pretty nice behavior versus annoying.

Yes, I need the remote sync option on the go.


  • Do you need to sync between machines – especially desktop Macs – in different geographic locations?
  • Do you have a colleague, assistant, significant other, etc. that needs frequent updates to synced data?
  • Are you using a shallow sync, i.e., Download Files: On demand in DEVONthink To Go?

If the answer is no to any of these questions, a local sync on your network is suggested.

Thanks for your suggestion and insights. I understand that DT should not be used when the requirements are

  1. syncing changes made to the database to multiple devices instantly
  2. over any network connection (WAN, LAN)
  3. in the background (whenever possible)

I’m coming from Evernote where this usually worked without any issues. Of course there have been glitches and conflicts in notes to be resolved, but at least I’ve been able to not bother ensuring that devices are running in the same network.

If you really are serious about using it, I think you need to do a bit more reading about how DEVONthink works. It’s a distributed database, with a copy on each device you put it on. It does not sync “instantly”. Hardly anything in the world is “instant” and with something like DEVONthink that not really important for the vast majority of users. Syncing does work across WANs and LANS if normal bandwidths available. And the synching does occure in “background” on those devices.

DEVONthink does not communicate directly with databases on other devices, unless you are using Bonjour.

It has been years since I used Evernote. I abandoned it when I realised that my stuff is held inside it’s databases in some sort of proprietary way, not available for my access without Evernote. For me, it’s very valuable that I don’t use a system that holds my data hostage and unavailable.

DEVONthink Bonjour sync works well–quickest and most reliable. I notice it’s almost instant if I add a doc on my iMac and it shows up on the MacBook very quickly. Also working well is DEVONthink synching with WebDAV and Dropbox. Apple’s servers are not up to it for DEVONthink (and based on other reports on the Internet) for other apps either. I have no experience with other synch methods and do not plan to take time from my use of my documents to do any testing.

Sounds like, with your requirements and perhaps erroneous assumptions, you are better off sticking with Evernote.

1 Like