Image Optimization - BoostPro Docs

Local WebP and AVIF conversion with quality presets, bulk optimization, auto-optimize on upload, and automatic delivery.

Overview

BoostPro converts your JPEG and PNG images to WebP and AVIF formats using your server's built-in GD or ImageMagick library. No external API, no cloud service, no per-image fees. Everything runs locally on your server, and original files are always preserved.

Converted images are stored in /wp-content/boost-images/uploads/, mirroring your uploads directory structure. A database table (wp_boost_images_meta) tracks per-image conversion status and file sizes.

Enabling image optimization

Go to BoostPro → Images tab and toggle Image Optimization on. This reveals all image optimization settings organized into three sections: Settings, Delivery, and Bulk Optimization.

AVIF conversion

AVIF is a separate toggle that can be enabled independently. AVIF produces smaller files than WebP (typically 20-40% smaller) but requires more server resources and specific library support.

Important

AVIF conversion requires PHP 8.1+ with GD AVIF support or ImageMagick 7.0+. If your server does not support it, enable WebP only.

Image library selection

BoostPro can use either GD Library or ImageMagick for image conversion:

Auto (default): Prefers ImageMagick when available (generally faster and better quality), falls back to GD
ImageMagick: Force ImageMagick for all conversions
GD: Force GD Library. Use this if ImageMagick causes issues on your server

BoostPro auto-detects available libraries on activation. Use the Detect button on the Images tab to refresh capability detection.

Quality presets

A single preset maps to the optimal quality value for each format. AVIF achieves equivalent visual quality at lower numbers than WebP:

Preset	WebP quality	AVIF quality	Best for
Lossless	99	80	Photography sites where quality is critical
High	90	65	Portfolio and design sites
Balanced (default)	80	55	Most websites (good quality with meaningful size reduction)
Aggressive	65	45	Content-heavy blogs and news sites
Maximum	50	35	Maximum compression where file size matters most

Tip

Balanced quality preset is recommended for most sites. It provides good compression with minimal visual difference.

Auto-optimize on upload

When enabled, BoostPro automatically converts images to WebP (and AVIF if enabled) as they are uploaded through the WordPress media library. This includes all registered image sizes: thumbnails, medium, large, and any custom sizes from your theme.

Skip if larger

Enabled by default. If a converted file is actually larger than the original (which can happen with already-optimized PNGs or small images), BoostPro automatically discards the converted file. You only keep converted files that are genuinely smaller.

Image resizing

Optionally resize oversized images before conversion. If an uploaded image exceeds your configured maximum width or height, BoostPro scales it down before creating the WebP/AVIF version.

Default max: 2560px width, 2560px height
When to use: When users frequently upload photos straight from cameras at 4000px+ dimensions

Delivery methods

BoostPro serves optimized images to visitors automatically. Choose the delivery method that matches your server:

Auto (recommended)

Detects your server type automatically and picks the best method. Apache and LiteSpeed get .htaccess rules. Everything else gets picture tags.

.htaccess rewrite (Apache/LiteSpeed)

Adds rewrite rules to wp-content/uploads/.htaccess that check the visitor's browser Accept header. If the browser supports AVIF and an AVIF file exists, it is served first. Otherwise, WebP is served if supported. The URL does not change, so there is nothing to update in your content.

Picture tags (Nginx/universal)

Wraps <img> tags in <picture> elements with AVIF and WebP <source> elements. The browser picks the best format automatically (AVIF first, then WebP, then original). Works with all servers including Nginx.

Exclude patterns

Exclude specific images from conversion by adding file path substrings to the exclusion list, one per line:

/logo
/favicon
/og-image

Any image whose file path contains a matching pattern will be skipped during both auto-optimize and bulk optimization.

Add missing image dimensions

Images without explicit width and height attributes cause layout shifts as the browser discovers their size after loading. This hurts your Cumulative Layout Shift (CLS) score.

This is a separate toggle, independent from image conversion. When enabled, BoostPro automatically adds missing width and height attributes to images in your page content.

Default: Off
Supported formats: JPEG, PNG, and SVG (with viewBox)
Smart sizing: If an image has one dimension set but not the other, BoostPro calculates the missing dimension proportionally from the original aspect ratio

Bulk optimization

The Bulk Optimization section scans your media library for unoptimized images using cursor-based pagination (100 images per batch). Optimization runs in batches of 5 images at a time with real-time progress counters.

Optimize All Images: Scans and converts all unoptimized JPEG and PNG images to WebP (and AVIF if enabled)
Delete All Converted: Removes all WebP and AVIF files from the boost-images directory. Original images are untouched.

Media Library integration

When image optimization is enabled, BoostPro adds a custom column to the WordPress Media Library showing per-image optimization status:

Savings percentage and file sizes for optimized images, showing format and size reduction
Optimize button for unoptimized images, to convert that individual image without running a bulk operation
Delete Optimized link below the savings stats, to remove the converted files for that specific image