WordPress Image Optimization Plugin — Asteris Image Optimization

Why does WordPress need an image optimization plugin? Images are typically 50-80% of a page’s total weight. Unoptimised images directly hurt Core Web Vitals (LCP especially), eat bandwidth, and slow mobile users. An image optimization plugin compresses images without visible quality loss, converts to modern formats (WebP, AVIF) that are 25-50% smaller than JPEG/PNG, and serves the right format to each browser.

What’s the difference between WebP and AVIF? Both are modern image formats. WebP (released 2010, mature, ~95% browser support) is typically 25-35% smaller than equivalent JPEG. AVIF (released 2019, growing support ~93%) is typically 40-50% smaller than JPEG and often beats WebP. Asteris generates both and serves whichever the visitor’s browser supports.

Can Asteris optimize my existing image library? Yes — bulk-optimise runs through every image in your media library, compresses each, generates WebP + AVIF versions, and stores them alongside the original. Old uploads benefit from the same compression as new ones.

The complete feature set

Compression

• JPEG compression — adjustable quality (default 82, range 60-100)
• PNG compression — lossless via pngquant-equivalent; ~30-50% size reduction with no visible quality loss
• Custom quality per image type (set higher quality for hero images, lower for thumbnails)

Modern formats

• WebP conversion — automatic for every image, alongside the original
• AVIF conversion — automatic for every image (paid tier)
• Format negotiation — Asteris serves the smallest format the visitor’s browser supports (via <picture> element with srcset fallbacks)
• Manual format override per image (e.g. force JPEG for compatibility)

Bulk optimization

• Bulk-optimise existing library — runs in the background; doesn’t lock WP Admin
• Per-batch limit (default 50 images per cron run) to avoid host CPU/memory limits
• Resume on interruption — if the cron job dies mid-batch, resumes from the last completed image

On-upload optimization

• Automatic on every new upload — original is kept, optimised + WebP + AVIF versions generated immediately
• WP Media Library integration — see optimization status per image
• One-click re-optimise per image with different settings

Lazy loading

• Native loading="lazy" on <img> tags
• Per-post-type rules (e.g. eager-load on landing pages, lazy elsewhere)
• fetchpriority="high" on the LCP image (coordinates with the Performance module)
• Exclusion rules for above-the-fold images

EXIF stripping

• Remove EXIF metadata from uploads (geolocation, camera info, edit history)
• Privacy + size reduction (typically 5-15 KB per image)
• Per-post-type rules (some sites want EXIF preserved, e.g. photography portfolios)

Retina (2x) generation

• Auto-generate 2x versions for retina/HiDPI displays
• Served via srcset so non-retina users don’t download 2x assets

CDN integration

• Cloudflare Polish + Mirage — Asteris signs off on aggressive Cloudflare image optimization (knows when to defer to CF)
• Bunny.net Stream + CDN — image variants
• Generic CDN URL rewriter — point image URLs at any CDN domain
• Image CDNs — Cloudinary, ImageKit, Bunny Optimizer (URL-based transformation)

Free version

Asteris for WordPress Free includes a lite version: bulk JPEG/PNG compression, on-upload optimisation, WebP conversion, before/after comparison. The full module (AVIF, CDN integration, lazy-loading rules, EXIF stripping, retina generation) is paid.

Frequently asked questions

Is there a free WordPress image optimization plugin? Yes — Asteris for WordPress Free includes WebP + bulk compression. Smush Free is also competent at the basic compression layer. EWWW Image Optimizer Free is another solid free option. For AVIF + CDN integration + retina generation, you need a paid tier.

What’s the difference between WebP and AVIF? Both are modern image formats smaller than JPEG/PNG. WebP (~95% browser support) is typically 25-35% smaller than JPEG. AVIF (~93% support, growing) is typically 40-50% smaller than JPEG and often beats WebP. Asteris generates both and serves whichever the browser supports.

Will optimization hurt image quality? Not visibly at default settings (JPEG quality 82, PNG lossless). You can lower quality further if you want smaller files; you can raise it for hero images. Side-by-side comparison is built into the admin.

Can I optimize images I’ve already uploaded? Yes — bulk-optimise runs through your existing library, compresses each, and generates WebP + AVIF versions. Originals are kept (so you can re-optimise with different settings or revert).

Does Asteris work with Cloudflare Polish or Bunny Optimizer? Yes — Asteris coordinates with both. If you have Cloudflare Polish on, Asteris defers to it for delivery-time optimization while still generating local WebP/AVIF for any non-Cloudflare delivery paths.

Will optimization break my images? No — originals are always preserved. If anything goes wrong, you can roll back per-image or in bulk.

Free version on WordPress.org → · Performance module → · Pricing →