Description

Pipe9 Media Optimizer converts your uploaded images to WebP automatically — no batch jobs, no manual steps, no complex configuration. When a browser supports WebP (all modern browsers do), the optimized version is served instead of the original, reducing page weight by 25-35% on average with zero visible quality loss.

How it works:

When you upload an image to WordPress, the plugin creates a WebP copy and stores it alongside the original in uploads/pipe9-media-optimizer/webp/. When a visitor loads a page, the plugin detects browser support via the Accept header and serves the WebP version — either through server-level rewrite rules, HTML markup, or a lightweight PHP endpoint.

Key features:

Automatic conversion on upload — JPEG, PNG, and static GIF images are converted to WebP as soon as they hit the media library. Animated GIFs are converted to animated WebP via gif2webp or Imagick (previously a Pro feature — now free!)
Six serving strategies: Apache rewrite rules (zero PHP cost — the fastest option), HTML <picture> wrapping (single buffer scan per page), Nginx config snippet (paste and go — includes theme image rules), PHP passthru endpoint (works on any server), WP Engine optimized mode, or conversion-only mode (no serving changes)
Theme image conversion — scans and converts images inside active theme directories
Bulk conversion — convert your entire existing media library with one click, with a real-time progress bar
Media Library integration — each image gets a format column showing WebP status, with per-image convert and remove actions
Memory guard — automatically detects when an image is too large to convert without blowing through PHP’s memory limit, and skips it gracefully
Pluggable architecture — modules register themselves via WordPress hooks; the Pro add-on adds AVIF and animated format support through the same system

Pro add-on (separate purchase from pipe9.uk) adds:
* Static AVIF conversion (JPEG/PNG/GIF AVIF) — even smaller files than WebP
* Animated AVIF conversion (animated GIF animated AVIF via ffmpeg)

Screenshots

Plugin settings page with serving strategy selection

Media Library with format column and row actions — Plugin settings page with serving strategy selection

Installation

Upload the pipe9-media-optimizer folder to /wp-content/plugins/
Activate the plugin through the Plugins screen
Go to Settings Pipe9 Media Optimizer
Choose your serving strategy (Auto-detect works for most setups)

FAQ

What image formats are converted?: JPEG, PNG, and static GIF images are automatically converted to WebP. Animated GIFs are now also converted to animated WebP in the free version (via gif2webp binary or Imagick). For animated AVIF conversion, use the Pro add-on.
How much will this reduce my image sizes?: Typical savings are at least 25-35% compared to JPEG, and at least 15-25% compared to PNG. Lossy WebP at quality 80 is visually indistinguishable from the original JPEG but substantially smaller. Lossless WebP preserves PNG transparency with smaller file sizes.
Does this work with my hosting provider?: Yes. Apache rewrite mode generates static .htaccess rules with zero PHP overhead — it’s the fastest option. Nginx and WP Engine modes show ready-to-paste config snippets. A PHP passthru mode works on any server, including locked-down hosts that don’t allow .htaccess overrides.
Will this affect my existing images?: No. Only newly uploaded images are converted automatically. Use the Bulk Convert tool on the settings page to convert your existing media library. You can also convert existing images one by one in the media listing section.
How do I verify it’s working?: Check the “Formats” column in Media Library list view — it shows which WebP copies exist. Or use browser DevTools to inspect response headers (look for Content-Type: image/webp).
Does the Pro add-on require a separate installation?: Yes, the Pro add-on is a separate plugin that requires Pipe9 Media Optimizer (free) to be installed and active.

Reviews

There are no reviews for this plugin.

Contributors & Developers

“Pipe9 Media Optimizer” is open source software. The following people have contributed to this plugin.

Özgür Altunyurt

Translate “Pipe9 Media Optimizer” into your language.

Interested in development?

Browse the code, check out the SVN repository, or subscribe to the development log by RSS.

Changelog

1.5.2

Fixed double .webp.webp bug — on_media_edited() now checks MIME type via get_post_mime_type() instead of file extension, preventing re-conversion of images already converted to WebP by WordPress core
Intermediate sizes loop now checks $size['mime-type'] to skip WebP thumbnails from WordPress core conversion
Upload pipeline switched from hardcoded extension whitelist to MIME-based detection (image/* except image/webp) — future-proof for any image source format

1.5.1

Refactored option prefix handling — removed dynamic $prefix/$option_prefix variables from all register_setting() calls, replaced with hardcoded module prefixes (e.g. p9mo_webp, p9mo_avif, p9mo_animated_avif)
Removed get_option_prefix() method and option_prefix format key
Removed $prefix parameter from register_extra_settings() in all modules

1.5.0

Animated GIF WebP now in free version — animated GIFs are converted to animated WebP inline via gif2webp binary (preferred) or Imagick coalesceImages() fallback (previously required the Pro add-on)
Theme images now served via passthru/picture instead of themes .htaccess — simpler, fewer rewrite rules, works on all server types
Nginx config output now includes theme image location blocks with try_files fallback
Extracted all inline JS to external files (media-actions.js, serving-settings.js, bulk-convert.js) — ~700 lines of PHP-built JS eliminated
Bulk convert UI consolidated into one parameterized JS component (replaces 4 near-duplicate per-module implementations)
Resolved WordPress.org and PluginCheck review issues (translators comments, option prefix uniqueness, ABSPATH guards, heredoc elimination)

1.4.3

cwebp binary support — Google’s command-line WebP encoder is now auto-detected and preferred over Imagick/GD for artifact-free high-quality output
Fixed WebP block artifacts (‘dots’, ‘crunchy’ look) at high quality settings — Imagick now uses webp:method=6, webp:auto-filter, webp:preprocessing=2 for smooth gradients
Fixed bulk convert pagination hole — no longer stops when page 1’s posts all have WebP files from previous single converts
Fixed silent conversion failure when exec() is disabled — detect() now checks P9MO_CAN_EXEC before selecting cwebp

1.4.2

Theme image conversion — automatically scans and converts images in active theme directories
Improved output buffer handling — skips AJAX, cron, and XML-RPC requests
Bug fixes and stability improvements

1.4.0

Initial release of the refactored plugin with pluggable module architecture
Pro add-on support with AVIF, Animated WebP, and Animated AVIF modules

Description

Screenshots

Installation

FAQ

What image formats are converted?

How much will this reduce my image sizes?

Does this work with my hosting provider?

Will this affect my existing images?

How do I verify it’s working?

Does the Pro add-on require a separate installation?