WebP Image Converter & Replacer

WordPress stores more than just the single file you see in the Media Library. For every image it also creates several thumbnail sizes, so the **true footprint** is:

(original file + thumbnails)

When WebP Image Converter & Replacer shows savings it compares the *combined* size of those originals with the *combined* size after conversion:

(original file + thumbnails) − (WebP file + WebP thumbs) = space saved

Because thumbnails often add up to more kilobytes than the original, the reported savings can exceed the size of the single file you uploaded—this is expected and accurate.

With this plugin’s default behavior, if a browser that doesn’t support WebP (e.g., an old version of Internet Explorer or an outdated Safari) tries to load an image that has been converted, the image may not display. In 2025, this is a very small subset of users (less than 5-10%). If your audience includes such users and you cannot afford them not seeing images, you have a few options:

• Use a WebP polyfill JavaScript (such as WebPJS) to enable those browsers to display WebP – however, note this may not cover all cases (and can’t fix unsupported <img> src without a fallback source).

• Alternatively, do not use this plugin on sites where legacy browser support is critical. Or, convert selectively (e.g., maybe skip converting images on pages catering to those users).

• In practice, many sites choose to serve WebP to everyone and ignore legacy browsers, given the performance gain for the majority. If you’re unsure, monitor your analytics for browser usage. (Future versions of this plugin may include an option to keep originals as a fallback, but the current version is “all-in” on WebP.)

The plugin uses WebP’s default compression (lossy with quality ~80-85 by Imagick’s internal settings). This typically produces a file much smaller than a JPEG of comparable quality. In most cases, visual quality remains high – WebP is designed to maintain quality at smaller sizes. The plugin doesn’t individually let you tweak quality settings in this version (it chooses a sensible default). If your original images were very high quality, the WebP will also be high quality but smaller. If your originals were already aggressively compressed, the WebP might not be much smaller (in which case, as noted, the plugin will keep the original to preserve quality). No additional blur or downscaling is applied – dimensions remain the same, and we preserve any embedded color profiles. We recommend you upload reasonably optimized images (e.g., don’t upload gigantic 100% quality JPEGs straight from a DSLR; resize/compress a bit first for best results).

Yes. The plugin adds a “Convert to WebP” action in the Media Library (list view) for individual images. You can convert one-by-one if you like. Or use the bulk convert tool to convert everything. In the bulk tool, you can also filter by date or by image size if needed (for example, convert older images first, or only convert images above a certain file size). This gives you granular control.

Currently, the plugin operates on the Media Library images (and their thumbnails) only. If there’s an image you do not want converted, you can simply skip it (don’t run conversion on that image). If you have a folder of images outside the media library, those are unaffected by this plugin (we intentionally focus on the media library to avoid impacting other files).

Converter for Media and WebP Express are popular plugins for WebP. They keep your original files and serve WebP via alternate means (either by rewriting URLs or using the tag approach). Our plugin’s philosophy is different: by removing originals, we save disk space and simplify your media library (you don’t end up with two files for every image). This is a manual, one-time (per image) operation rather than an ongoing dynamic conversion. The benefit is no runtime overhead and maximum storage saving, but the trade-off is no automatic fallback. It’s geared toward sites ready to embrace WebP fully. It also doesn’t require complex server rules or additional caching layers to serve WebP – once converted, your site is literally running on WebP images directly.

It shouldn’t negatively affect SEO. In fact, faster page loads can improve SEO. The plugin updates the image URLs to .webp, but the image ALT text, titles, and captions remain the same (those are what impact SEO). If your images were being indexed as .jpg URLs, they will eventually update to the new .webp URLs. Major search engines like Google can index WebP images just fine. Make sure to update your XML image sitemaps (if any) after conversion, so they list the new file URLs. In short, you trade the old URLs for new ones – but since the content (the image) is equivalent and on the same site, this is a neutral change for SEO, with the upside of improved site performance metrics.

Yes. WordPress generates multiple thumbnail sizes (small, medium, large, etc.) for responsive image srcsets. The plugin will convert each of those thumbnails to WebP and update the attachment meta data. Your front-end tags will continue to have a srcset with multiple image sizes – except now they all end in .webp. This means responsive images still work perfectly (the browser picks the appropriate size, and since it supports WebP, it will load the WebP files). Just be aware that those additional thumbnails are also subject to deletion of originals – which is intended, as it saves space.

A few possibilities:

• Some images might not have been converted if the WebP wasn’t smaller. The plugin will report “Skipped X images because WebP was larger” in the summary. Those images remain as original format, so no space saved there. If you still want them in WebP (e.g., for uniformity), you could enable an option like “force convert” (though that might not be available yet – or you’d have to manually convert those with higher compression externally).

• If you have a caching plugin or CDN, the old images might still be counted until cache is cleared. But on disk, they should be gone. Check your /uploads/ folder via FTP – do you see .jpg files still? If so, those were likely not converted on purpose.

• Also, remember if you had backup plugins or an uploads backup, those won’t be cleared by this plugin. Only the active Media Library files are touched.

Not really. That message means those specific images (often small icons or already compressed photos) didn’t benefit from WebP. They remain as is (JPEG/PNG) so your site will still serve them in original format. It’s actually a good thing – it means the plugin ensured you wouldn’t end up with a larger file. The overall impact is minor if only a small percentage are skipped. You can optionally try compressing those originals further (with a tool or plugin) and then run the convert again to see if WebP becomes smaller.