I'm having the same issue after upgrading to MacOS 10.13.3 and using the latest illustrator (22.0.1). Adobe take note of your user's comments and provide seamless implementation of illustrator basic functions before adding superfluous (and sometimes outright silly) content to the interface. After so many updates basic node selection is still shoddy, and overall the program is more unstable than ever. Cut the clutter or go down as the new Corel draw phenomenon.... :-)

I have the same issue with the error "this file has been modified outside of Illustrator," even though it has 100% NOT been modified outside of Illustrator. The issue began immediately after I upgraded to High Sierra 10.13.3. My files have always been backed up on Dropbox and no other user has access to these files but me. I never had this issue before the upgrade and I'm using the same files from the same location. (I use CS6 so please do not tell me to upgrade to CC. Our company is too small to pay an extravagant monthly fee for 2 users). Please fix ASAP! Thank you.

I also have this issue. I only have Illustrator open - no other Adobe products or other third-party programmes. The only adjustment I made was to save the changes to the file as 'Save As' and rename it as a 'v2'. This has been occurring since I upgraded to High Sierra. I'm working off our local server, but I've been doing that for the last 15 years.

Funny how you continuously shove the CC Library syncing down our throats but still can't get the basics right - I've seen this issue in threads going back to 2012.

Yes, just got the new macbook pro and this just started happening. Not using dropbox files or google drive, everything is on my hard drive. The files have 100% NOT been modified outside of Illustrator.

I also get this problem when saving to a normal disk. Mac OS 10.13.3

I work with files saved to Google Drive and I get this message in Illustrator — not every time I go to save, but quite frequently.
When it does happen, the file has definitely not been modified outside of Illustrator.
I work with files on my hard drive and synch to Google Drive: I had assumed that perhaps I get the message when the synching is in progress?

Been happening ever since the upgrade to 10.13.3. Also I have to keep resetting Photoshop files to popen with Photoshop. Daily issue for both.

I've been getting the same message in various files, for a week or two.

I recently upgraded OS to 10.13.2, but that was over a month ago, so not clear it correlates to OS update.

It also seems to be random or intermittent - I only ********* certain files, and sometimes I DO NOT get that same message on same files!

And no, the file was not edited online or on a different computer, etc.

I'm having this issue as well. My files are stored, edited, and saved on my local drive.

Same issue as everyone else... Not saving to dropbox, no external drives. Everything stored locally... Hope a fix is determined soon...

I too started getting this after High Sierra and CC updates. Working locally, iMac 10.13.3, not using Fonts. It happens every time I manually save, and every time it auto-saves.

I am having the same issue. On files going to iCloud, Dropbox and files only on my Hard Drive. I do not have iCloud Drive set to backup all files. No matter if the images are embedded or linked, and layers locked or unlocked. Everything I save with Illustrator issues a warning of modified outside of illustrator. I created a test file with only linked and embedded images from my hard drive with the same result.

I find if you lock all your layers before saving it's fine :)

Started happening to me just today after updating to 10.13 His Sierra. According to this thread this has been going on since November?!

This error was a normal part of my routine about a couple of years ago. I remember it had something to do with a version of Suitcase. Illustrator was sensing that Suitcase had modified the file (fonts)? In my experience, this does not occur in a file that does not contain type.

It only happened to me when I opened an Illustrator file with an embedded jpeg. It didn't happen with a linked jpeg.

After updating to Siera, Illustrator CS5.1 keeps crashing every time i try to use fonts. I also get the same message "this file has been modified outside illustrator" when i try to save my work. I can't even preview fonts in the font panel. Adobe has stopped updating older software regardless if you paid $1500 for the creative suite because they want to force people to buy their subscription service.

I think the Adobe company has turned into a awful greedy company that cares more about their shareholders than their actual products and customers. I'm a graphics designer, photographer and web designer that works with 10 other artists and we' ll make sure to let everyone know how horrible this company has become. No more Adobe.

I am getting this too, just updated to High Sierra. I am a production artist, this issue is IMPORTANT.

I'm getting this error too:
Mac OS X 10.13.2 (17C205), Illustrator 22.0.1.

I am also having this issue after upgrading to OS 10.13 (High Sierra). I am on Illustrator 20.0.1 and am saving my files to the local drive.

I save my files multiple times throughout working on them, but the error only shows up every couple of saves. During this time the file will be open in Illustrator, not being used by any other programs (that I know of). Sometimes I will need to switch to the login screen while away from my desk, but that is the closest I get to actually "closing" the files the whole time I'm working on them.