How-to Guide 2 min read

How to Compress Images for WordPress

WordPress does not compress images by default — it only resizes them to create thumbnail sizes. This means every unoptimised image you upload stays large. The smartest approach is to compress and convert images before uploading, so WordPress never sees the bloated versions. Pre-optimising takes 30 seconds per image and can improve your Google PageSpeed score by 20–40 points.

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By ImgToolkit Team · Updated May 2026 · 2 min read · Processed in your browser

PNGJPGWebPGIFBMP

Quick Answer

WordPress does not compress images by default — it only resizes them to create thumbnail sizes. This means every unoptimised image you upload stays large.

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Step-by-Step Guide

5 steps · takes under 1 minute

Convert to WebP before uploading

WordPress 5.8+ supports WebP natively. Converting JPGs and PNGs to WebP before upload gives 25–35% smaller files with no visual quality difference. Use the Convert from JPG tool to switch formats.

Resize to display dimensions

WordPress generates thumbnails but still serves the full-size original for large image blocks. Resize blog images to 1200px wide (2400px for retina) before uploading. Product images: 1000–1500px square.

Compress to 80% quality

Drop your WebP or JPG into the compressor. Target under 200 KB for blog content images, under 500 KB for hero/banner images, under 100 KB for thumbnails.

Upload the optimised files to WordPress

Upload your compressed, resized, correctly-formatted files to the Media Library. WordPress generates the required thumbnail sizes from your already-optimised originals.

Test with Google PageSpeed Insights

Run your post/page URL through PageSpeed Insights. 'Serve images in next-gen formats' and 'Properly size images' warnings should be cleared. LCP should improve noticeably.

Before vs After Compression

Typical result on a 1080×1080px product photo

Before 4.2 MB

📷 Original PNG

→

After 820 KB

🗜️ −80% smaller

Before: 4.2 MB — slow to load, rejected by email

After: 820 KB — fast loading, visually identical

🔒

100% Private — Zero Uploads

ImgToolkit runs entirely in your browser using the Canvas API. Your images are never sent to a server, never stored in the cloud, and never seen by anyone else. This makes it safe for sensitive documents, client work, medical imagery, and confidential screenshots.

💡

Pro tip

Use 75–85% quality for web images — you get 60–80% smaller files with no visible difference at normal screen sizes.

Format & File Size Comparison

Same 1080×1080px photo processed four ways

Format	Quality	File Size	Notes
PNG (original)	Perfect	4.2 MB	No compression — too large for web
Compressed PNG	Visually identical	1.1 MB	−74% — transparency preserved
JPG (85% quality)	Excellent	310 KB	−93% · Best for photos
WebP (85%)BEST	Excellent	205 KB	−95% · Recommended for web

Based on a 1080×1080px photo. Results vary by image content and complexity.

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PNG → JPG

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Frequently Asked Questions

4 questions answered

Should I use a WordPress image compression plugin or compress manually?

Manual pre-compression (using ImgToolkit) gives you more control and avoids the recurring API costs charged by plugins like Smush Pro, Imagify, and ShortPixel. The tradeoff is time — plugin automation is faster if you upload many images per week. For most small sites and blogs, pre-compression is the better approach.

What is the best image size for WordPress?

Blog post featured images: 1200×630px (also correct for og:image). In-content images: match your content column width, typically 800–1200px. Product images: 1000×1000px square. Hero/banner: 1920×1080px. In all cases, compress to under 200 KB before uploading.

Does WordPress compress images on upload?

WordPress applies a default 82% JPEG quality to images it resizes (when generating thumbnails). The original uploaded file is stored uncompressed. This means your full-size images are served at their original (uncompressed) size unless you pre-compress them or use a plugin.

My WordPress site scored 40 on PageSpeed. Can image compression fix it?

Image optimisation typically accounts for 20–40 PageSpeed points on image-heavy sites. Other factors include server response time, JavaScript, CSS, and caching. Fixing images is the highest-impact single action but won't alone get a poor-performing site to 90+. Address render-blocking scripts and enable browser caching alongside image optimisation.

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Compress for WordPress

Image Compressor

Free · Browser-based · No account

Compress for WordPress

Privacy First

Your images are processed entirely in your browser using WebAssembly. No files are ever uploaded to a server.

What's included

Compress JPG, PNG, and WebP

Target specific file size goals

Before/after file size display