Does WordPress convert old images to WebP?
Since WordPress 5.8 you can upload a .webp file into the Media Library the same way you upload a JPEG. That upload does not walk the library and rewrite files already there. A module that converts on upload, including the WebP option in the Performance Lab plugin, only affects the next JPEG you add.
Creating one WebP in a browser or on your computer, then uploading it, replaces that one attachment if you swap it by hand. It is not a bulk conversion. Exporting a page to PDF is a different job and does not change image formats.
Which method converts the library?
Use one image plugin for the files already uploaded. Do not turn on a second plugin that also rewrites the same images. Two converters fight, and the page can serve a broken picture or a JPEG you thought was gone.
| Method | What it converts | Stop when |
|---|---|---|
| One image plugin, bulk run | JPEG and PNG already in the Media Library, then new uploads. | Save image as on a live photo says WebP. |
| WebP on upload only | The next JPEG you add. | Older library files are still JPEG. |
| Upload a WebP made elsewhere | That one attachment, if you swap it by hand. | The rest of the library is unchanged. |
| Terminal conversion | Only the files you point the command at. | The binary or Imagick is missing, or the browser still gets a JPEG. |
On shared hosting, stay with the plugin. A terminal conversion needs a WebP-capable binary and a PHP library such as Imagick. If the plugin says the server cannot write WebP, email support@webji.services with the error. Do not delete the JPEG copies until the browser test passes. The office phone is not the support line.
How do you bulk-convert the Media Library?
Take a backup of wp-content/uploads first, or a full account backup. The usual plugin keeps the JPEG and writes a WebP beside it. The backup is the undo if a logo looks soft.
Stop when a photo on the public site saves as WebP. Stay logged in while the bulk job runs.
- Open Plugins, then Add New. Search for ShortPixel Image Optimizer. Click Install Now, then Activate. Paste the API key the plugin asks for and save. A screen with a compression choice means it is on.
- Set compression to Lossy for photographs. If the library is mostly logos or screenshots with text, choose Lossless so the edges stay sharp.
- Turn on creating WebP versions and delivering them. On Nginx, or when a CDN caches images, choose picture-tag delivery instead of an Apache rewrite. Save.
- Open the plugin bulk screen and start the queue. Leave it until the count of remaining images is zero. New uploads should convert without another bulk run.
- Do not activate a second WebP plugin while this one is running.
ShortPixel asks for an API key, and a free allowance can run out on a large library. When the queue stops, pay that vendor or turn the plugin off and use one other converter.
A WebJi® hosting invoice does not include this plugin. If you want the desk to run the conversion, email support@webji.services and the quote arrives before you pay.
How do you confirm the browser got WebP?
Open a published post that uses an old photo. Right-click the image and choose Open image in new tab. Then right-click and choose Save image as. The file type in that dialog should say WebP.
The address can still end in .jpg. Some plugins keep the original URL and swap the bytes. Trust the save dialog, or the Type column in the browser Network panel after a reload, not the letters in the URL.
If the type is still JPEG, change delivery from rewrite rules to picture tags, save, and purge any CDN cache. Apache rules in .htaccess do nothing on Nginx. Run the save-as test again in a private window so an old cached JPEG does not fool you.
What still looks wrong after conversion?
A smaller file is not a faster page by itself. WebP often cuts a photo by about a quarter of its weight at a similar look. The plugin report lists the bytes it actually saved. If the largest image is still huge, resize it.
Lazy load in WordPress waits to fetch images below the fold. It does not convert them.
WebP is not higher quality than the JPEG you started with. At the same file size it usually looks cleaner. At the same look, the file is smaller. Heavy lossy settings soften text in screenshots. Use lossless for those.
- Very old browsers may not show WebP. Leave the plugin's JPEG fallback on so those visitors still get a picture.
- Email and some print tools still want JPEG or PNG. Keep the originals.
- Two optimizers, or a CDN that compresses again, can make a photo blurry. One converter is enough.
- A slow theme or a distant server still hurts Largest Contentful Paint. Images are only one part of that score.
Sites on WordPress hosting can run this plugin on the plan you already have. If the library is large and you want someone to resize, convert, and retest the page, that work is WordPress speed optimization, quoted by email before you pay. It is not included just because the site is hosted here.
Frequently Asked Questions
How do I convert WordPress images to WebP?
Install one image plugin such as ShortPixel, turn on WebP creation and delivery, and run the bulk queue on the Media Library. New uploads convert after that. Confirm with Save image as that the type is WebP.
Does WordPress support WebP images?
Yes. Since WordPress 5.8 you can upload a WebP file. WordPress does not convert JPEG and PNG files already in the library. That conversion is a plugin or a server tool.
Is WebP better quality than JPG?
Not by itself. At a similar file size, WebP usually looks cleaner than JPEG. At a similar look, the WebP file is smaller. A harsh lossy setting can look worse than the original JPEG.
What are the disadvantages of WebP?
A few old browsers need a JPEG fallback. Some email and print tools cannot open WebP. Lossy settings soften text in screenshots. Conversion does not resize a huge image or fix a slow theme.
Will converting to WebP delete my JPEG files?
A normal image plugin keeps the JPEG and adds a WebP copy. Do not delete the originals until Save image as shows WebP. Turning the plugin off lets the site serve the JPEG again.
How do I create a WebP image without a plugin?
Export it from your image editor, or convert that one file in the browser, then upload the WebP. The rest of the Media Library stays JPEG or PNG until you run a bulk conversion.