SlashImage – Image Optimizer: Compress Images, Convert WebP & AVIF

Your images are almost certainly the heaviest thing on your website. They slow down every page, which can hurt your search rankings and frustrate visitors. SlashImage fixes that automatically, the moment you hit upload.

Install it. Paste your free API key. That is the entire setup. From that point on, every image you add is compressed, converted to WebP and AVIF, and served in the right format for each visitor. Automatically, in the background.

Typical sites see image file sizes drop by 80 to 90%, with no visible difference in quality.

Smart Optimization Tuned to Each Image

Instead of applying one fixed quality setting to every image, SlashImage analyzes each image and reduces its file size while keeping it visually close to the original, so you get smaller files without a visible drop in quality.

⚡ Completely Automatic, From the Second You Upload

Upload an image and SlashImage gets to work in the background instantly. Your upload never waits. Your media library never blocks. New posts, pages, and products simply start loading faster, with nothing for you to click.

Want manual control? Switch off auto-optimize and run images yourself. By default, it just works.

Smart Features

Smart Backups: Full Safety, Less Disk Space
Smart Backups stores only your original image, not a copy of every generated thumbnail. When you restore, each thumbnail is regenerated automatically from that original — full protection while using less disk space.

Automatic PNG to JPEG Conversion
Photos saved as PNG can be many times larger than they need to be. SlashImage analyzes each PNG and converts it to a lighter JPEG only when the image will genuinely benefit, such as a photograph with no transparency. Illustrations, flat-color graphics, and logos are left as-is, so you get smaller files with no downside and nothing to manage yourself.

Precision Exclusions
Keep specific images untouched. Exclude individual thumbnail sizes, or skip any image whose filename or path matches your own rules.

🎚️ Three Compression Modes for Every Kind of Site

• Lossy (recommended) The smallest files, with quality differences that are very hard to see. A good fit for blogs, businesses, and WooCommerce stores.
• Glossy High-fidelity compression that protects fine photographic detail. Made for photographers and portfolios.
• Lossless Zero quality loss, for when you need pixel-perfect originals.

📦 Optimize Your Entire Library in One Click

Already sitting on thousands of images? Open Media to Bulk Optimize, click Start, and walk away. SlashImage works through your whole media library in the background, every image and every thumbnail, while you get on with your day. Pause, resume, or cancel any time. Close the tab and it keeps going.

🛡️ Your Originals Are Always Safe

Every original is backed up before SlashImage changes a thing. Restore any image with one click from the Media Library, the attachment screen, or restore your whole site at once from Settings. Changed your mind about anything? It is one click back.

🎯 WebP and AVIF, Served Automatically to Everyone

SlashImage creates WebP and AVIF copies of every image and serves each visitor the most efficient format their browser supports. AVIF is typically smaller than WebP at the same quality. Browsers that support it get it, and everyone else gets a fallback, so images always display. Animated GIFs are converted to animated WebP too, often much smaller while keeping the animation intact.

No server config required for most sites. Prefer server-level delivery? SlashImage supports Apache .htaccess rules and gives you ready-made Nginx snippets too.

🏢 Built for Agencies and Multiple Sites

• A separate key per site. Generate sub-keys at slashimage.com, each with its own independent usage tracking.
• Your billing stays private. Plans, credits, and account details are never shown inside the plugin. Your clients only ever see the stats for their own site.
• Full Multisite support. Every subsite runs with its own key, queue, and settings.

✅ Works With Your Whole WordPress Stack

Built to play nicely with your themes, page builders, and plugins, including WooCommerce, Elementor, Yoast SEO, WP Rocket, W3 Total Cache, WP Super Cache, Cloudflare, and WordPress Multisite.

🚀 Lighter Images, Faster Pages

Lighter images can mean faster pages and better Core Web Vitals scores, for a smoother experience for every visitor. SlashImage gets you there without you touching a single setting.

Get your free API key at https://slashimage.com

External services

This plugin connects to the SlashImage API (https://api.slashimage.com) to compress and optimize your images, which cannot be done locally by the plugin. When an image is optimized (on upload, during a bulk run, or on re-optimize) it is sent to the API and the optimized version is returned and saved to your site; the original is deleted from the API servers immediately after processing. The plugin also contacts the API to verify your API key when you connect it. Each request includes your API key and your site address (sent in the Origin header, so the API can honor keys restricted to specific domains); no page URLs or other personal data are sent. Your use of the API is covered by its terms of service (https://slashimage.com/terms-of-service) and privacy policy (https://slashimage.com/privacy-policy).