Kraken.io Image Optimizer – Compress, Convert to WebP & AVIF, Resize & Bulk Optimize

⚡ 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. Kraken.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. Every upload is sent to Kraken.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. At its heart is Kraken.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. (For security, raw SVG upload is intentionally not enabled — see the FAQ.) ⚡ Built for Core Web Vitals Heavy images are the number-one cause of slow pages. By compressing every size, converting to WebP/AVIF and right-sizing oversized uploads, Kraken.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. Every action is protected by nonces and capability checks, uploads are content-verified, and all optimization happens server-to-server with Kraken.io. No secrets ever reach the browser. 🚀 Get started for free

Create a free Kraken.io account — no credit card required — and get testing quota to try the plugin and the rest of the Kraken.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.

★★★★★ 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. It is a perfect solution as is." — collin ★★★★★ Quality results, quality service "The plugin works really well and effortlessly, and the support is prompt, thoughtful, and thorough. I'm hooked." — illustrata ★★★★★ Optimize according to Google PageSpeed "Kraken was instrumental in optimizing images to comply with Google's PageSpeed analyzing tool. Our travel blog now sports Google's 'mobile friendly' tag for mobile searches." — 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. Highly recommend!" — ezone69

Connect with Kraken.io

• Website: https://kraken.io
• Plans & pricing: https://kraken.io/pricing
• Twitter / X · Facebook · GitHub

You can be optimizing images in a couple of minutes — no servers to configure and no command line.

1. Install the plugin. From your WordPress admin, go to Plugins → Add New, search for Kraken.io Image Optimizer, then click Install Now and Activate. (Prefer to do it manually? Upload the plugin folder to /wp-content/plugins/ and activate it from the Plugins menu.)
2. Create your free Kraken.io account. Sign up here — no credit card required, and you get testing quota to try the plugin right away.
3. Copy your API credentials. Open your API Credentials page and copy your API Key and API Secret.
4. Connect the plugin. Back in WordPress, go to Settings → Kraken.io, paste your API Key and API Secret, choose your optimization preferences, and click Save Changes. A green check confirms your credentials are valid.
5. That's it. Every image you upload from now on — and all of its generated thumbnails — is optimized automatically. To compress images already in your library, use the Bulk Optimize with Kraken.io screen under Media, or the Optimize button in the Media Library list view.

3.0.3

• New: the plugin is now translated into 64 locales, covering 39 languages — Albanian (Shqip), Arabic (العربية), Belarusian (Беларуская), Bosnian (Bosanski), Bulgarian (Български), Chinese (中文 — Simplified, Traditional and Hong Kong), Croatian (Hrvatski), Czech (Čeština), Danish (Dansk), Dutch (Nederlands — Netherlands and Belgium), Estonian (Eesti), Finnish (Suomi), French (Français — France, Canada and Belgium), German (Deutsch — informal, formal, Austrian and Swiss), Greek (Ελληνικά), Hebrew (עברית), Hungarian (Magyar), Icelandic (Íslenska), Indonesian (Bahasa Indonesia), Italian (Italiano), Japanese (日本語), Korean (한국어), Latvian (Latviešu), Lithuanian (Lietuvių), Macedonian (Македонски), Norwegian (Norsk — Bokmål and Nynorsk), Polish (Polski), Portuguese (Português — Portugal, Brazil and Angola), Romanian (Română), Russian (Русский), Serbian (Српски), Slovak (Slovenčina), Slovenian (Slovenščina), Spanish (Español — Spain, Mexico, Argentina, Chile, Colombia, Costa Rica, Dominican Republic, Ecuador, Guatemala, Honduras, Peru, Puerto Rico, Uruguay and Venezuela), Swedish (Svenska), Thai (ไทย), Turkish (Türkçe), Ukrainian (Українська) and Vietnamese (Tiếng Việt).
• New: a "Savings on this site" panel on the Stats screen — a clear breakdown of how much your full-size images and their thumbnails were each reduced (from how much, to how much), calculated from your own data and kept separate from the shared account quota.
• New: a sticky "Save Changes" bar on the settings screen with a live "unsaved changes" reminder, so edits — especially a freshly pasted API key and secret — are never lost by forgetting to save.

3.0.2

• Security: tightened permission checks so users can only optimize, convert or reset media they are allowed to edit.
• Fixed: files without thumbnails (PDFs, AVIF, small images) are now handled correctly — they optimize and show their savings, and no longer report a false error or keep reappearing in the Bulk Optimize list.
• Fixed: optimization failures now report the real reason (e.g. a timeout or a missing file) instead of a generic "Unknown error."
• Fixed: free accounts that reach their test quota now see an upgrade prompt instead of an inaccurate paid-plan billing notice.

3.0.1

• Performance and reliability improvements to the Kraken.io API connection, with broader server compatibility.

3.0.0

• New: optimization support for WebP, AVIF, HEIC, HEIF and PDF (in addition to JPEG, PNG and GIF).
• New: convert uploads to WebP, AVIF, JPEG, PNG or GIF on the fly, synced live between the Media panel and settings.
• New: a Kraken.io control panel on the Media Library, Add Media and Plugins screens, plus a Dashboard widget — showing connection status, plan, quota usage, active settings and supported formats.
• New: a dedicated Bulk Optimize with Kraken.io screen, reachable from the Media menu, the Media Library and the panel.
• New: per-image savings and error badges in the Media grid and list, updated live as images optimize.
• New: conflicting-optimizer detection with one-click deactivation of other image plugins.
• New: "Who can optimize images" capability setting (all logged-in users by default).
• New: a Support tab linking to the WordPress.org forum and a pre-filled email, with copyable diagnostics.
• Security: API key and secret are now write-only and masked — never pre-filled or exposed in the page source; nonce and capability checks on all AJAX actions; uploads are content-verified; raw SVG upload disabled as an XSS precaution.
• Change: the large 1536×1536 and 2048×2048 retina sizes are now off by default to save quota (filterable; existing choices are respected).
• Change: legacy WebP companion options are deprecated in favour of Convert.
• Fix: a now-resolved error no longer keeps showing an error badge after a successful re-optimization.
• Fix: the bulk count now lists only supported image formats (no more HTML/other files).
• Fix: division-by-zero when calculating savings on PHP 8; assets are cache-busted by file modification time.

2.7.0

• Complete plugin rewrite with a modular OOP architecture.
• Added WebP image generation and display support.
• Added background processing for image optimization.
• Added support for WP Retina 2x, NextGen Gallery and WP Offload Media.
• Security: capability and nonce checks on the reset-all AJAX handler; input sanitization; whitelist validation for the settings tab parameter.
• Requires PHP 5.6+ and WordPress 4.9+.

2.6.6

• Security release to solve https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-38454

2.6.0

• Added the ability to choose which image sizes get optimized.
• Added the ability to change the chroma subsampling scheme for JPEG images.
• Stability and compatibility improvements.

2.5.0

• Optionally disable optimization of the main image for faster uploads.
• Restrict the maximum dimensions of uploads (resizing), with sharpening enhancement.
• Force a discrete JPEG quality value; preserve selected EXIF tags; auto-orient by EXIF.

2.0.0

• Kraken.io settings moved to their own section (Settings → Kraken.io) with grouped Advanced Settings.

1.0.3

• Added the "Krak 'em all" bulk optimization feature to the Media Library Bulk Actions menu.

1.0

• First release: lossy and lossless optimization of JPG, PNG and GIF (including animated GIF), with automatic optimization of uploads and their thumbnails. For the full version history of older releases, see the plugin's WordPress.org changelog.