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'PDF' recognize as 'MP3', 'PNG/JPG' recognize as 'Unknown' file type

We are using GroupDocs.Metadata (License Type - Site OEM - paid version). We are able to clean metadata for most of the file extensions like (docx, pptx, mp3, txt, csv, xlsx) but failing for PDF, PNG, JPG extensions.

Listing the errors for each file type below-

  • PNG/JPG - Unexpected file format type: Unknown
  • PDF - Unexpected file type: Mp3


  1. We are doing this metadata cleanup inside a docker container (Linux container - Ubuntu bionic image).
  2. Separately for testing purpose we created one console utility (on windows machine) there PDF/PNG/JPG files metadata cleanup is working fine (tried SkiaSharp.NativeAssets.Linux 2.88.3 package as well - it did not help).


  • Docker container - Linux - Ubuntu Bionic image
  • .Net Framework - 4.7.2
  • GroupDocs version - Latest stable 23.1.0
  • Xamarin - XamarinBionic 18.04

Attaching docker file and PDF/Image cleaner code snippets as well.

Any help/pointers would really appreciate.Code files.zip (1.9 KB)

We have opened the following new ticket(s) in our internal issue tracking system and will deliver their fixes according to the terms mentioned in Free Support Policies.

Issue ID(s): METADATANET-3992

You can obtain Paid Support services if you need support on a priority basis, along with the direct access to our Paid Support management team.



  • We logged the assembly version since we thought it could be using an older version of the GroupDocs DLL due to a cache issue, but it is using the correct version 23.1.0
  • We verified upgrading Ubuntu version from bionic (Ubuntu 18.04.6 LTS) to focal (Ubuntu 20.04.5 LTS)

image.png (7.6 KB)

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Thanks for the details. We’ll continue the investigation.

Hello @atir.tahir - I could use some advice on this. Any additional alternatives we can attempt on our end while you respond. Thanks!


Your ticket is still under investigation. We’ll notify you as soon as we have any fix or workaround.

Any new information on this topic, @atir.tahir? Do you require any more information? This problem has us bogged down. We need to reprocess some old file upload (in azure blobs format) that are in Azure Blobs format. Could you provide an update on this?


We are still investigating this issue for .NET framework (e.g. 4.7.2). But if you use .NET 5, .NET 6, or .NET Core 3.1, then the error is not reproduced.

@atir.tahir - sharing few more findings with of GroupDocs metadata (two different versions) DLL and .NET framework version 6-

image.png (15.3 KB)

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We’ll continue our investigation and let you know in case of any update.