AEM Dynamic Media: forcing PNG output when images are delivered as WebP

Last update: October 22, 2026

If images from Dynamic Media presets configured for PNG output are still delivered as WebP, add both fmt=png and bfc=off to the preset. Adding only bfc=off does not force PNG output.

Description description

Environment

Adobe Experience Manager Dynamic Media (all versions)

Symptoms

Dynamic Media presets are configured to output images as PNG.
When downloading or viewing images in a browser, the files are delivered as WebP instead of PNG.
Adding only the bfc=off parameter in the preset configuration does not resolve the issue; images continue to be served as WebP.
Adding bfc=off directly to the image URL results in the image being delivered as PNG as expected.

Cause

Smart Imaging’s Browser Format Conversion (BFC) feature automatically delivers images in modern formats like WebP unless explicitly disabled. Adding only bfc=off disables browser format conversion, but does not force PNG output. The fmt=png modifier is also required to explicitly set the output format.

Resolution resolution

Try the steps below to resolve the issue.

Edit the affected Dynamic Media preset in the Scene7 configuration.
In the preset’s URL modifiers, add both fmt=png (or fmt=png-alpha if transparency is required) and bfc=off to explicitly set the output format and disable browser format conversion:
- For PNG: fmt=png&bfc=off
- For PNG with transparency: fmt=png-alpha&bfc=off
Save and publish the updated preset.
Clear the CDN cache or allow time for the cache to expire before retesting the download.
To verify, download or view an image using the updated preset and check the Content-Type header in the HTTP response; it should be image/png.
Ensure that no additional fmt or bfc parameters are appended to the final image URL, as these could override the preset values.

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