Mimetype change from application/vnd.adobe.illustrator to application/pdf if more then 10 artboards

[Davide5EC7]

Hi, there's a strange behavior regarding mimetype when saving an .ai file with more then 10 artboards.

Checking the mimetype using exiftool, if the .ai has more then 10 artboards, its mimetype is application/pdf. If there are fewer artboards, its mimetype is application/vnd.adobe.illustrator. This data is used later in an internal flow, so it is important that the mimetype is consistent.

The file is saved in a local folder, and it can be replicated by just creating a new document from scratch. I've tried to save it with or without 'toPdf' conversion but nothing changed.

AI version: 27.8

Replicated either on Mac and Window machine.

I've attached the screenshot of the log for either mimetype. Adding or removing the last artboard you could replicate the behavior.

It's a bug or some kind of internal limit regarding how AI file are saved? 

Thank you

[Anubhav M]

Hello @Davide5EC7,

Sorry for the delayed response. I hope the problem is resolved by now. If not, kindly share more details, like the exact version of the OS/Illustrator, system config (CPU/GPU/Memory), and sample files (https://community.adobe.com/t5/illustrator-discussions/share-your-files-in-6-simple-steps/td-p/12967...), so we can investigate this further?

Looking forward to hearing from you.

Thanks,

Anubhav

[Davide5EC7]

Hi, the problem is already here.

I’ve prepared some data, 10_artboard.ai, and 11_artboard.ai with 10 and 11 artboards inside, and the screenshot of the metadata of those 2 files. 

https://shared-assets.adobe.com/link/5dd96ee4-9d0a-406f-4e85-d71163acf870 

From your shell use the command

exiftool <filename>

And check the result. 

10_artboard.ai (correct file)

• File type: AI
• File type Extension: ai
• MIME Type: application/vsn.adobe.illustrator
• XMP Toolkit: Adobe XMP Core 9.1
• Format: application/pdf

11_artboard.ai (incoherent metadata)

• File type: PDF
• File type Extension: pdf
• MIME Type: application/pdf
• PDF version: 1.6
• XMP Toolkit: Adobe XMP Core 9.1
• Format: Application/pdf

Both of this are generated From Adobe Illustrator 27.8 (I've tried also on 27.7) and have the same error.

I’ve tried it on Mac OS with the following configuration:

• Montrey (12.2) with exiftool 12
• Big Sur (11.4 ) with exiftool 11
• Ventura (13.5) with exiftool 12.4

We’ve done also a test on a Window machine, but the result was the same (I don’t have the machine specification) 

[Anubhav M]

Hello @Davide5EC7,

Thanks for sharing the sample files and details about the problem. Kindly allow me some time to check this with the team.

Thanks,
Anubhav

[Anubhav M]

Hello @Davide5EC7,

Thanks for your patience, and sorry for the delayed response. Would you mind confirming if you are using the latest version of the EXIF Tool (12.65)?

Looking forward to hearing from you.

Thanks,

Anubhav

[Davide5EC7]

Hello Anubhav Majumder,
I just tried again on a Mac using the latest version of exiftool, v12.67, released on September 19, 2023,  and the results are the same.

[Anubhav M]

Hello @Davide5EC7,

Thanks for sharing the info. Kindly allow me some time to check this with the team.

Thanks,

Anubhav

[Anubhav M]

Hello @Davide5EC7,

Thanks for your patience. I was unable to replicate this behavior on my end. Would you mind sharing some background on why this EXIF data is required? Also, EXIF is used to capture Camera Data like Camera Make/Model, Lens used, etc. (https://en.wikipedia.org/wiki/Exif). A PDF (or an Ai file) does not have EXIF data. Instead, the metadata is contained in XMP (ISO 16684-1).

Looking forward to hearing from you.

Thanks,

Anubhav

[Davide5EC7]

Hello,
for security reasons, we use exif primitives to make sure that the file used in upload streams to our external software is actually an .ai file type and not some other renamed file type.

The procedure I showed you above, so from the command line write for example exiftool 10_artboards.ai , allows you to verify the metadata that is prepared, and this is where there is the discrepancy shown above.

Using the two files I attached above, if you don't want to use exiftool you can try mime (https://github.com/broofa/mime#readme) or you can tetst the behavior on some online mimetype checker (such as https://jimpl.com/ or https://www.metadata2go.com/view-metadata), and the behavior can be replicated.

The 10_artboard file returns an application/vnd.adobe.illustrator mimetype and AI filetype, while the 11_artboard file returns an application/pdf mimetype and PDF filetype.

We tried possibly relying on the magic numbers, but the AI files would indicate a PDF type file in both cases (https://asecuritysite.com/forensics/magic)

I hope this information will be helpful to you!

Thank you