MegaOptim Image Optimizer – Convert to WebP & AVIF, Compress Images Locally

MegaOptim optimizes the images of your WordPress site on your own server. It creates WebP and AVIF copies of your JPEG, PNG and GIF images, serves them to browsers that support them, and can compress the originals in place. Nothing is uploaded anywhere, and there are no monthly limits.

What it does

• WebP and AVIF copies of every image and thumbnail size, kept next to the original. A copy that would be larger than the original is skipped.
• Delivery through <picture> markup or Apache/LiteSpeed rewrite rules, with the original as the fallback for older browsers. A CDN URL can be set for the copies.
• Compression in place for JPEG and PNG, with three presets: Lossless, Balanced and Smaller files. Advanced settings hold separate WebP and AVIF quality, resizing of large uploads, metadata and the thumbnail sizes to process.
• Backups and restore. Originals are backed up before they are changed, and any image can be restored, one at a time or all at once.
• Bulk optimization of the whole Media Library with one button. It runs in the background, survives closing the page, and shows its progress on the Overview and in Activity.
• New uploads are optimized automatically.
• Folders outside the Media Library, such as theme or plugin image folders.
• Compare an original with its optimized version side by side.
• WP-CLI: wp megaoptim optimize, restore, status and stats.
• Diagnostics that show which image engines your server offers and what each one can do.

How images are processed

MegaOptim uses what your server already has: the GD or Imagick PHP extensions, and command-line encoders such as cwebp, avifenc, jpegtran, pngquant, oxipng or gifsicle when your host has them installed. The plugin itself contains no executables. AVIF needs GD or Imagick built with AVIF support, or avifenc. Tools → Server diagnostics shows what is available on your server.

MegaOptim Pro

MegaOptim Pro is an optional add-on. It brings its own native engine for Linux (MozJPEG, libwebp, libavif, oxipng, pngquant, gifsicle), which compresses noticeably better than GD or Imagick and turns animated GIFs into animated WebP. Its smart quality picks the lowest quality for each image that still looks the same, measured with SSIMULACRA 2. Pro also optimizes media offloaded to S3-compatible storage with S3 Uploads or WP Offload Media, and adds parallel WP-CLI and network-wide tools for multisite. Images are still processed on your server.

Source code

The admin screens are a Vue application. Its source is included in the plugin’s admin folder and is built with bun install && bun run build.

1. Install and activate MegaOptim Image Optimizer.
2. Open Media → MegaOptim.
3. On Settings, pick a preset and the formats to create (WebP, AVIF or both). Tools → Server diagnostics shows what your server can do.
4. Optimize a few images on the Images screen and compare them with the originals.
5. Click Optimize library on the Overview to process everything else. New uploads are optimized automatically.

1. 

   Overview: library coverage, space saved and one button to optimize the whole library.

2. 

   Images: every image with its savings and formats, filterable by status and source.

3. 

   Compare an original with its optimized version.

4. 

   Settings: a quality preset, the formats to create and optimization of new uploads.

5. 

   Advanced settings: WebP and AVIF quality, resizing and metadata.

6. 

   Activity: background work as it happens.

7. 

   Tools and diagnostics: restore everything, and see what your server can do.

3.0.0

• All optimization now runs on your server. The cloud API, API keys and image credits are gone.
• A redesigned admin: Overview, Images, Settings, Activity and Tools, with one Optimize action for compression and WebP/AVIF.
• Settings presets (Lossless, Balanced, Smaller files) with separate WebP and AVIF quality.
• Better JPEG output with Imagick and GD: progressive encoding, optimized Huffman tables, and never a higher quality than the source.
• Originals are backed up before every change, for media and folder images, and restore no longer re-optimizes the restored file.
• Native encoders keep a photo’s embedded color profile, so photos from cameras and editors no longer fall back to Imagick.
• A new background queue: atomic claims, two images at a time, and progress that continues when the page is closed.
• WebP and AVIF copies that would be larger than the original are recorded as such instead of being retried.
• Offloaded media is detected and skipped with an explanation instead of failing.
• WP-CLI: wp megaoptim optimize, restore and status.
• The plugin no longer contains executables; it uses GD, Imagick and tools installed on the server.
• Upgrades from cloud versions keep settings, history and backups, remove the stored API key and pause pending cloud work for review.

2.0.2

• File System view: Convert and Compress now work on folders and single files, with live progress.
• Fix: Convert no longer drops thumbnail siblings. Every thumbnail size now produces its own WebP and AVIF file.
• Fix: forced re-convert kept the freshly converted files instead of wiping them at the end of the run.
• Polished folder modal (mode-aware hero, force re-process toggle, cancel-during-run, per-file failure list).

2.0.0

• Complete refactor of the plugin (Vue 3 admin, modern PHP architecture, new conversion engine for WebP/AVIF, File System view, queue monitor, WP-CLI commands).
• Backwards compatible: legacy v1.x mode remains available and existing settings and attachment data are migrated in the background.

Older versions are listed in changelog.txt.