About this plugin
⚡ Compress, resize and convert your WordPress images to WebP, AVIF and more — automatically. Faster pages, smaller files, same quality.
Slow pages cost you visitors, search rankings and sales — and over-sized images are almost always the culprit. io Image Optimizer fixes that on autopilot: it compresses, resizes and converts every image you upload — and every thumbnail WordPress generates — so your whole site loads lighter and faster, without you lifting a finger.
io, one of the most advanced image-optimization APIs on the web, optimized in the cloud, and pulled straight back into your Media Library. No binaries, no command line, no server tweaks — install it, add your API key, and stop worrying about heavy images.
io’s intelligent lossy engine: for every single image it finds the exact point where the file is as small as possible while staying visually indistinguishable from the original. Expect to cut 60% or more off your image weight — exactly the win Google PageSpeed and Core Web Vitals reward.
From a personal blog to a busy WooCommerce store with tens of thousands of products, it’s an install-and-forget solution that just works.
✨ Why Kraken.io
- Intelligent lossy & lossless — pick maximum savings with no visible quality loss, or pixel-perfect lossless. Per-image JPEG quality and chroma subsampling control for power users.
- Convert between formats — turn uploads into WebP, AVIF, JPEG, PNG or GIF. Reach for next-gen WebP or AVIF for the biggest savings (and to clear Google’s “Serve images in next-gen formats” audit), or switch between the classics — whatever fits your site.
- Optimizes everything WordPress serves — the full-size image and every thumbnail size (thumbnail, medium, large, …) that actually reaches your visitors through responsive srcset.
- PDFs too, not just images — PDF files in your Media Library are compressed through the same Kraken.io engine, so documents download and embed faster.
- Smart resizing — cap oversized uploads to a maximum width/height; resized images are enhanced to stay sharp and avoid haloing.
- Bulk “Krak ’em all” — optimize your entire existing library from a dedicated Bulk Optimize screen or the Media Library bulk action, with live progress.
- A control panel that tells you everything — a Kraken.io summary panel on the Media Library, Add Media and Plugins screens (plus a Dashboard widget) shows your connection status, plan, quota usage, active settings and supported formats at a glance.
- Per-image savings & error badges — see exactly how much each image saved, right in the Media grid and list.
- Plays nice with your stack — works with multisite, page builders, CDNs and local/dev sites. Detects other optimizer plugins and offers one-click deactivation so they don’t fight over your images.
🖼️ Supported formats
JPEG, PNG, animated GIF, WebP, AVIF, HEIC/HEIF and PDF. )
⚡ Built for Core Web Vitals
Heavy images are the number-one cause of slow pages. io directly targets the audits that move your score: Properly size images, Efficiently encode images, Serve images in next-gen formats and Largest Contentful Paint.
🎛️ Your images, your control
- Choose intelligent lossy or lossless, globally.
- Convert uploads to WebP/AVIF/JPEG/PNG/GIF on the fly — synced live between the panel and settings.
- Preserve selected EXIF tags (Date, Copyright, Geotag, Orientation, Profile) or strip them for the smallest files.
- Auto-orient photos from phones and cameras by their EXIF orientation.
- Decide who can optimize — all logged-in users, authors and up, or administrators only.
- Pick exactly which image sizes to optimize (the large 1536×1536 and 2048×2048 retina sizes are off by default to save quota — turn them on if your theme serves them).
- Optimize on upload automatically, or defer and bulk-optimize later.
🔒 Private & secure by design
Your API credentials are stored write-only and masked — they are never pre-filled into the page or exposed in your site’s source, so other users on the dashboard can’t read them. io. No secrets ever reach the browser.
🚀 Get started for free
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io toolset:
- A fully-featured optimization API with official libraries for PHP, Node.js, Python, Ruby, Java, Go and.NET
- Web Interface (free) and Web Interface PRO with resizing and sync-to-Dropbox
- URL Paster and Page Cruncher to optimize images in bulk from anywhere on the web
- Optimization history and stats, and Kraken.io Cloud Storage
You can use a single API key across as many sites as you like — there is no per-site license.
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★★★★★ Excellent option for image optimization
“The real power of Kraken is their ‘intelligent lossy’ optimization. I use it on all my sites and have never once needed to roll back an image because of too much quality degradation. ” — collin
★★★★★ Quality results, quality service
“The plugin works really well and effortlessly, and the support is prompt, thoughtful, and thorough. ” — illustrata
★★★★★ Optimize according to Google PageSpeed
“Kraken was instrumental in optimizing images to comply with Google’s PageSpeed analyzing tool. ” — Walter Schaerer
★★★★★ Perfect solution to speed up site!
“I love this plugin! All my questions are quickly responded to and I see a huge saving in image size without losing quality. ” — ezone69
Connect with Kraken.io
- Website: https://kraken.io
- Plans & pricing: https://kraken.io/pricing
- Twitter / X · Facebook · GitHub