How to Compress PNG Online – Free PNG Compressor

PNG is a lossless image format, which means it stores all pixel data without throwing any away. That is why PNG files are sharp and clean — and also why they tend to be large. When you need to compress PNG online, you are not removing pixel data but rather optimizing how the file stores that data.

Why PNG files are large

PNG uses lossless compression, which means the algorithm encodes the exact pixel values without approximation. For photographs and complex images with millions of color variations, this creates very large files. For simpler graphics with flat areas of color, PNG compresses very well.

A typical smartphone photo saved as PNG might be 8–12 MB. The same photo as a high-quality JPG might be 1–2 MB. If you need to keep the PNG format but reduce file size, the approach is to compress the metadata, reduce the color palette, or convert to a more efficient format like WebP.

How to compress PNG online with Resizo

• Step 1: Open Resizo in your browser at resizo.in.
• Step 2: Drop your PNG file onto the tool or click to browse.
• Step 3: If file size is the priority, switch the output format to WebP — this typically reduces file size by 25–35% compared to PNG while maintaining excellent quality.
• Step 4: If you must keep PNG output, resize the image to smaller dimensions first. Reducing a 2000px wide PNG to 800px wide reduces file size dramatically.
• Step 5: Download the compressed result.

PNG compressor: when to use PNG vs WebP vs JPG

Choosing the right format is the most effective way to compress PNG:

• Keep PNG when: You need transparency (alpha channel), you need pixel-perfect lossless quality (logos, UI assets), or the receiving system only accepts PNG.
• Switch to WebP when: You're optimizing for web delivery, you want both transparency support and small file size, and the browser/platform supports WebP (all modern browsers do).
• Switch to JPG when: The image is a photograph without transparency, you need the broadest format compatibility, and you're willing to accept slight lossy compression.

How much can you compress a PNG?

The compression ratio for PNG depends heavily on image content:

• A simple logo or icon with flat colors can compress to 10–20% of its original size using optimized PNG encoders.
• A photograph saved as PNG will compress to 80–90% of its original size at best, because photographs have very little redundancy to exploit.
• Converting a photograph PNG to WebP typically reduces file size by 25–35%.
• Converting a photograph PNG to JPG (high quality) can reduce file size by 60–80%.

Lossless vs lossy PNG compression

True lossless PNG compression (like pngcrush or zopfli) re-encodes the file using a more efficient algorithm without changing any pixel values. This typically achieves 5–20% reduction. It is safe and ideal for production assets where quality cannot change.

Lossy PNG compression (like pngquant) reduces the color palette, which can achieve 40–70% reduction with minimal visible change on most images. This works best for icons, illustrations, and screenshots rather than photographs.

For most web use cases, the practical solution is to compress PNG online by converting to WebP, which is natively supported in all modern browsers and achieves better results than lossy PNG compression.

PNG file size reduction tips for web developers

• Serve WebP format with a PNG fallback for older browsers using the HTML <picture> element.
• Resize PNGs to their display dimensions before serving — a 3000px PNG displayed at 300px wide wastes 90% of its data.
• Use lazy loading for below-the-fold PNG images to improve page load performance.
• Consider using SVG for logos and icons instead of PNG — SVG is resolution-independent and often much smaller.