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Sreeji_Lal
Sreeji_Lal
Level 2
September 24, 2026
Question

AEM Assets Dynamic Media: How to Replace an Auto-Generated PDF Thumbnail with a Custom Thumbnail Rendition?

I uploaded a PDF to AEM Assets with Dynamic Media enabled. A thumbnail is automatically generated, but the crop doesn't look good. I uploaded a custom image rendition in the required dimensions, however AEM continues to display the Dynamic Media-generated thumbnail instead of the custom rendition.

How can I configure AEM/Dynamic Media to use my custom thumbnail image for the PDF asset and override the default generated thumbnail?

4 replies

TarunKumar
Community Advisor
TarunKumarCommunity Advisor
Community Advisor
September 28, 2026

Hi ​@Sreeji_Lal ,
 

Below are the steps that you can take:-

 

Method 1: Using AEM User Interface

1.    Navigate to the uploaded asset for which you want to change the thumbnail.
2.    In asset selection mode, from either the List View or Card View, select the asset.
3.    Click on the Properties icon (a circle with an “i” in it) on the toolbar.
4.    On the asset Properties page, click on Change Thumbnail.
5.    On the Change Thumbnail page, you can either:
    o    Or, select Select Thumbnail from Assets from the toolbar. Navigate to a previously uploaded and published image asset that you want to use as the thumbnail. The chosen asset will be automatically resized to serve as a thumbnail image.
6.    Save the changes.

 

Hope it helps!

-Tarun

 

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Sreeji_Lal
Sreeji_LalAuthor
Level 2
September 28, 2026

Thanks for your response ​@TarunKumar .

I did try this, but I don't see the Change Thumbnail option in the new Assets UI. I can only see the uploaded thumbnail under Versions, and under Renditions I'm only able to download the available renditions.

I also tried uploading a custom rendition named cq5dam.web.1110.321, expecting it to be available for consumption in my application as the thumbnail. While the rendition gets created successfully, it doesn't seem to be picked up by the application.

As a workaround, I've currently created a separate Thumbnails folder, where I upload and manage thumbnail images independently, and maintain a mapping between the asset and its thumbnail in the database. This works for now, but it feels like there should be a more native AEM/Dynamic Media approach for associating custom thumbnails with assets.

Could this behavior be related to Dynamic Media assets, or is there another recommended way to expose a custom thumbnail rendition for external applications?

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AmitVishwakarma
Community Advisor
AmitVishwakarmaCommunity Advisor
Community Advisor
September 28, 2026

Hi ​@Sreeji_Lal 
One clarification: the documented Change Thumbnail workflow is for video assets, so it may not be available for PDFs. PDF previews are handled separately
https://experienceleague.adobe.com/en/docs/experience-manager-cloud-service/content/assets/dynamicmedia/custom-thumbnail
https://experienceleague.adobe.com/en/docs/experience-manager-cloud-service/content/assets/manage/manage-pdf-documents

Adding a rendition such as cq5dam.web.1110.321 makes it available, but does not automatically make AEM or your external application use it as the PDF thumbnail. The application would need to explicitly request that rendition, for example through the Assets Delivery API, or use a separate thumbnail asset mapped to the PDF.
https://experienceleague.adobe.com/en/docs/experience-manager-cloud-service/content/assets/dynamicmedia/dynamic-media-open-apis/deliver-assets-apis
If the application is showing a Dynamic Media-generated PDF preview, that may be separate from the static rendition. Could you share whether the application reads a rendition URL, an Assets Delivery API response, or a Dynamic Media URL? That will help narrow down the right approach.

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Amit Vishwakarma - Adobe Commerce Champion 2025 | 17x Adobe certified | 6x Adobe SME
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