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Custom Thumbnails and Previews with Quick Look on iOS |

Learn how to build your own Quick Look preview and thumbnail extensions to display custom file types in iOS.

This is a companion discussion topic for the original entry at

I’m trying to implement custom thumbnails and previews in my app. My extensions don’t ever seem to be run. I read through this tutorial, downloaded the code, and ran the final code sample, but it did not work for me either. I built it with both Xcode 12.3 and Xcode 12.5 beta, and I tried running on 14.4.2 and 14.5 devices and the 14.5 simulator. Neither the thumbnail extension nor the QuickLook preview are generated, no matter which scheme I run. I’m not able to trigger any breakpoints in the extensions. Do you have any idea why the sample app is not working for me?

@nc2000 Thank you for trying the tutorial. Sorry you are having some difficulties with getting the extensions to run. I tried again with the final project and am experiencing results similar to yours using Xcode 12.4. Unfortunately, this is an issue with Xcode. I’ve posted to Apple developer forums to see if anyone in the community has suggestions.

Thank you for looking into it!

Thank you for this great tutorial. In Xcode 13.0 beta 5 it works fine. I have a question: Is it possible to make custom thumbnail in document-based app using the same principles?

Absolutely. The exact same principles apply.