Custom Thumbnail Generator – Image Sizes, WebP & Media Usage

Custom Thumbnail Generator puts your images under your control: the sizes WordPress creates, the format visitors download, and where each image appears on your site.

Everything runs on your own server. There are no API keys, no monthly quotas, no external services and no upsells. Your original images are never changed, and every WebP setting can be switched off again at any time.

Image sizes that outlive your theme

• Add custom thumbnail sizes (width, height, hard crop) from a simple screen, without code.
• Sizes are stored by the plugin, not the theme, so they keep working when you switch themes.
• Regenerate a single custom size, or every thumbnail, for all images, with a live progress bar.
• Custom sizes appear in the block editor’s image size menu.

WebP: create, serve and automate

• Convert existing JPEG and PNG images and every thumbnail size to WebP, for the whole library, one size or one image.
• Serve WebP to visitors with one switch for all images, or image by image. URLs are swapped only in the pages visitors see. Nothing is written to your posts or database, so switching off restores the originals instantly.
• Only when it is smaller: a size whose WebP is larger than the original keeps the original.
• Automatic WebP for new uploads: every new JPEG or PNG gets WebP copies in the background, whether it comes from the Media Library, the editor, the REST API, WP-CLI or a plugin such as ACF.
• Self-healing: a daily check notices WebP files that went missing and switches those sizes back to the original.

Know where every image is used

The Attachment Summary page lists every image with the post it was uploaded to and every place it is actually used: post and page content, custom fields, page builders such as Elementor, featured images, galleries, WooCommerce product galleries, widgets, theme settings, the site logo and the site icon.

• Filter to images with no usage found, images that were never attached, or images not scanned yet.
• See the size of each image’s files, its WebP copies, the compression ratio and the disk space WebP saves.
• Preview any image in a pop-up, search by title or file name, and sort by title, type or number of places used.

Safe by design

• Original images, thumbnails and attachment data are never modified.
• WebP copies are deleted together with their image, so a deleted image does not stay online as WebP.
• GIFs are never converted, so animated GIFs keep their animation.
• Large libraries are processed in small batches from the browser, so no request runs long enough to time out.
• Deleting the plugin removes all of its settings and stored data.