The Cerious Software development cycle is notoriously slow. ThumbsPlus v10 was released years ago, and v11 has been "in development" for a long time. There is no official roadmap for deep WebP support, including:

If you are managing a large library of WebP images, the most robust solution is upgrading to .

The most reliable way to get WebP working in ThumbsPlus is to install a system-wide codec. This allows ThumbsPlus to "hand off" the file to Windows for rendering.

These versions were released before WebP gained traction. You cannot view thumbnails for WebP files, nor can you convert to/from WebP within the software.

When dealing with thousands of assets destined for web publishing, converting images to WebP saves massive amounts of bandwidth and significantly accelerates website loading speeds. The Core Challenge: ThumbsPlus and Native WebP Support

XnView MP is free software that reads WebP perfectly and writes to standard formats. Use it as your pre-processor.

If WebP files show as generic icons:

periodically updates support for modern web formats to remain competitive with other viewers. Solutions for WebP Integration

If you are running an older version of ThumbsPlus (v7, v8, or v9), you will likely encounter a "Unknown file format" error when trying to open a WebP image. The format simply did not exist in the mainstream when those versions were architected.