Local WebP optimizer for WordPress. Free converts images to WebP; Pro adds AVIF and site-wide image tools.
Alternatives to Slimbox
Plugins below are selected for functional relevance and current directory signals. Active-install counts do not affect this ranking.
Relevant replacements
WordPress plugins with similar use cases
Compatibility and update metadata provide context, not a quality guarantee. Review each plugin’s details for your site.
Automatically compress JPEG, PNG and GIF images on upload. Bulk optimize your media library, keep backups, and track savings per image.
OneTap WebP Converterv1.0.0
Convert all existing JPG/PNG images in your Media Library to WebP with a single click, in place, with no duplicates.
Only WebP Uploadsv1.0.1
Automatically converts uploaded images (JPG/JPEG/PNG/GIF) to WebP, including all WordPress sizes.
atec WebPv1.1.32
Auto convert all BMP, GIF, PNG & JPEG images into the much better WebP format. Supports the GD & ImageMagick libraries.
PixCompressv1.4.9
Compress JPEG, PNG, WebP, and GIF in the media library without changing URLs. Originals are backed up so you can restore anytime.
Scan your Media Library and convert JPG/PNG/GIF images to WebP for faster page loads — without touching your originals.
Automatically converts JPG and PNG images to WebP format, optimizes size to 100KB-115KB range, updates database URLs, and generates SEO alt text.
QODE Optimizerv1.2.3
The QODE Optimizer plugin is developed to allow you to convert, compress and adjust file sizes for all the images found on your website.
Comment Image Boostv1.0.16
Attach images to WordPress comments with drag-and-drop, preview before posting, admin moderation, and lightbox viewer.