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How to Use WebP Express with Pre-Existing WebP Images

34 threads Sep 9, 2025 Plugin → Webp express

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Many users migrate to the WebP Express plugin after already having a library of WebP images, perhaps generated by another plugin or service. A common question is whether WebP Express can recognize and use these pre-existing files instead of generating new ones, thereby saving server resources and time.

The Problem: Duplicate Conversions and Unused Files

By default, WebP Express is configured to convert images on the fly as they are requested by a visitor's browser. If you already have a complete set of WebP images, this default behavior is inefficient. It could lead to the plugin generating a second set of WebP files, wasting disk space and inodes, or it might not use your pre-existing images at all.

The Solution: Configure "No Conversion" Mode

Based on the sample threads, the WebP Express team has a built-in solution for this exact scenario. To make the plugin work with your pre-generated WebP files, you need to change its operation mode.

  1. Navigate to the WebP Express settings in your WordPress admin dashboard.
  2. Locate the Operation mode setting.
  3. Change it to "No conversion".

In this mode, the plugin's conversion functionality is completely disabled. It will not create any new WebP files. Instead, it assumes that for every JPEG or PNG file, there is a corresponding WebP file located in the exact same directory. The WebP file must have the same name as the original, with a .webp extension appended (e.g., image.jpg.webp). The plugin will then create server rewrite rules to seamlessly serve the existing WebP images to supported browsers.

Important Considerations

  • File Structure: Your pre-existing WebP files must be in the same folder structure as your original images for the plugin to find them. The "No conversion" mode does not use the separate "Image roots" destination structure.
  • New Images: A key limitation of this mode is that it will not automatically convert any new images you upload after enabling it. You will need to use your external conversion method to generate WebP files for new uploads and place them in the correct folder for the plugin to serve them.
  • CDN & Offload Compatibility: If you use a plugin like WP Offload Media to serve images from Amazon S3 or another CDN, ensure your WebP files are also offloaded to the same storage bucket with the correct path and file names for the redirection to work properly.

This configuration allows you to leverage the powerful serving capabilities of WebP Express while maintaining full control over the image conversion process itself.

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