Recently, I wanted to analyze an animated GIF directly within the Windows File Explorer Preview Pane. To my surprise, Windows doesn't natively support animated GIF previews there. While you can open the file in the built-in image viewer to play a GIF animation, it has notable limitations - you can't pause the animation or step through it frame by frame.

I remembered that Windows allows custom shell extensions, although I had never built one myself. So I took the opportunity to dive in, researched the necessary APIs, and began developing a preview handler that enables animated image previews directly in the File Explorer Preview Pane.

During this process, I came across two particularly helpful resources: "Preview Handlers and Shell Preview Host" and "Thumbnail Handlers." These guided me in implementing both a preview handler and a custom thumbnail provider.

Beyond animated previews, I also wanted to improve how thumbnails are generated. By default, Windows uses only the first frame of an animation as a static thumbnail, which is often not representative. To address this, I implemented logic to generate more meaningful static thumbnails for GIF, WebP, and APNG images.

The result is havPreviewHandler - a shell extension DLL for Windows 11 File Explorer that provides animated previews and representative static thumbnails for GIF, WebP, and PNG files (including APNG content in PNG containers).

The shell extension is released as freeware and is available on the havPreviewHandler project page.

The screenshot below shows havPreviewHandler displaying an animated GIF directly in the File Explorer Preview Pane: