PDEV Image Optimizer – WebP & AVIF

The goal is simple: generate modern image formats locally, reduce unnecessary image transfer, serve optimized images correctly, and provide enough diagnostics to understand when server configuration prevents optimization or delivery from working.

What does the plugin do?

PDEV Image Optimizer creates WebP or AVIF copies of images from the WordPress Media Library.

It can:

• Automatically optimize newly uploaded images.
• Convert an existing Media Library in small, restartable batches.
• Process WordPress thumbnail sizes.
• Optionally optimize supported images from the active theme.
• Scan for missing or obsolete thumbnails.
• Regenerate missing or all registered thumbnail sizes.
• Preview and clean obsolete PDEV-generated optimized files.
• Show storage savings and estimated transfer savings.
• Detect conflicting image plugins and rewrite rules.
• Test whether optimized images are actually delivered to visitors.
• Generate ready-to-copy Nginx configuration.
• Integrate optionally with Cloudflare.
• Provide a privacy-safe system report for troubleshooting.
• Run bulk optimization, cleanup, the delivery test, and settings changes from WP-CLI with wp pdevio .

You only need to choose:

• WebP or AVIF as the output format.
• Which source formats should be converted: JPEG, PNG, GIF, or WebP where applicable.
• Conversion quality.
• Whether new uploads should be optimized automatically.
• Whether supported images from the active theme should also be processed.

Main features

• Local WebP and AVIF image conversion with Imagick or GD.
• Automatic optimization of new WordPress uploads and generated thumbnails.
• Restartable bulk optimization of the existing Media Library.
• Optional optimization of supported images from the active theme.
• Thumbnail scan, missing-thumbnail repair, full regeneration, and obsolete-file cleanup.
• Cleanup that previews count and size before deleting only files whose name and location mark them as PDEV-generated ( image.jpg.pio.webp ).
• Cleanup modes for obsolete generated files or all PDEV-generated optimized files.
• Adjustable optimization speed, from a conservative shared-hosting profile to a fast profile for a VPS or dedicated server.
• Per-image safety limits that skip unsafe files without stopping the complete optimization job.
• WP-CLI command wp pdevio for optimization, targeted conversion, cleanup, status, the live delivery test, and format or speed changes.
• Storage usage and estimated transfer savings statistics.
• Apache and LiteSpeed delivery through managed .htaccess rewrite rules.
• Generated Nginx configuration for servers where WordPress cannot modify the web-server configuration directly.
• General image-plugin and rewrite-rule conflict detection.
• Optional Cloudflare Free-compatible cache integration.
• Live HTTP delivery test for WebP and AVIF responses.
• Detailed privacy-safe system report with copy and JSON export.
• Tested encoder support, server requirements, delivery status, and conflict checks, summarised on the main screen and detailed under System status.
• Actionable recovery instructions when a configuration check fails.
• Error history from the last 24 hours, limited to 50 entries.
• No external conversion service, telemetry, tracking, subscription, paywall, or PRO version.

How does image optimization work?

1. 01WordPress stores an image such as photo.jpg and usually creates thumbnail files such as photo-768x512.jpg .
2. 02PDEV Image Optimizer uses Imagick, or GD as a fallback, to create an optimized file next to each source file.
3. 03The optimized file is stored as a separate WebP or AVIF sidecar, for example photo.jpg.webp , photo.jpg.avif , or photo-768x512.jpg.webp .
4. 04The original image is not deleted, renamed, or replaced.
5. 05WordPress content continues using the existing URL ending in .jpg , .png , .gif , or .webp .
6. 06When a browser requests the original URL, the web server checks the browser’s Accept header.
7. 07If the browser supports the selected modern format and the optimized sidecar exists, the server returns WebP or AVIF instead.
8. 08Browsers without support receive the untouched original image.

This approach keeps existing WordPress URLs, post content, image references, and metadata unchanged.

Image delivery on Apache and LiteSpeed

On Apache and compatible LiteSpeed servers, PDEV Image Optimizer adds a clearly marked PDEV Image Optimizer block to .htaccess inside the uploads directory.

If theme image optimization is enabled, the plugin also manages a marked block inside the active theme directory.

The rules:

• Detect WebP or AVIF browser support.
• Serve the optimized sidecar when available.
• Set the correct MIME type.
• Add Vary: Accept so caches know that one URL can return different image formats.

The uploads directory and its .htaccess file must be writable when the plugin needs to add or update these rules.

Image delivery on Nginx

WordPress cannot safely edit Nginx server configuration.

PDEV Image Optimizer therefore generates ready-to-copy map and location blocks in System status .

A server administrator must:

1. 09Add the generated map block to the appropriate http context.
2. 10Add the generated location block to the correct server context.
3. 11Test the Nginx configuration.
4. 12Reload Nginx.

Conversion and delivery are separate steps. Successfully generated WebP or AVIF files do not guarantee that visitors receive them if the required server rules are missing.

Live image delivery test

The Settings overview includes an optional live delivery test.

When an administrator clicks Test image delivery , PDEV Image Optimizer:

1. 13Creates a temporary one-pixel source image and optimized sidecar inside uploads.
2. 14Requests the original source URL with the appropriate Accept header.
3. 15Checks the returned HTTP status and Content-Type .
4. 16Immediately removes both temporary test files.

A successful result confirms that the server is actually returning image/webp or image/avif .

The test runs only when an administrator starts it manually.

Server requirements

PDEV Image Optimizer needs both:

• A working PHP image conversion library.
• Correct web-server configuration for automatic delivery.

Installing the plugin cannot add missing PHP extensions or override restrictions imposed by your hosting provider.

Required for image conversion:

• WordPress 6.4 or newer.
• PHP 8.0 or newer.
• Imagick or GD installed and enabled in PHP.
• The selected image library must support the selected output format.
• WebP support does not automatically mean AVIF support.
• The WordPress uploads directory must be writable by PHP.
• The server must provide enough memory and execution time for the images being processed.

Required for automatic delivery on Apache or LiteSpeed:

• Apache-compatible rewrite support ( mod_rewrite ).
• MIME support ( mod_mime ).
• Header support ( mod_headers ). Without it the rewrite rules stay inactive, so caches never store an optimized file without Vary: Accept .
• .htaccess files must be allowed and processed for the uploads directory.
• On Apache, this normally requires an appropriate AllowOverride setting.
• The uploads directory or its existing .htaccess file must be writable by PHP when the plugin manages delivery rules.
• When theme image optimization is enabled, the active theme directory must meet the same requirements.
• If the site root .htaccess already has rewrite rules for the uploads or theme folder (for example a media protection plugin), PDEV does not write its own .htaccess there, because that would switch those rules off. System status shows the generated rules to add to the root .htaccess below the existing rules.

Required for delivery on Nginx:

• Access to the Nginx website configuration.
• Permission to add the generated map block to the http context.
• Permission to add the generated location block to the correct server context.
• Permission to test and reload Nginx after changing the configuration.
• Server-level add_header directives (HSTS, CORS) are not inherited by the generated location ; repeat them inside it. Deny rules for private upload folders must use location ^~ .

If you use managed hosting and do not have access to these settings, ask your hosting provider:

• Whether Imagick or GD supports WebP or AVIF.
• Whether the required Apache modules are enabled.
• Whether .htaccess overrides are allowed.

PDEV Image Optimizer cannot bypass server res