PNG is the go-to format for screenshots, icons, and anything with a transparent background. The catch? PNG files are often far larger than they need to be. In this guide you'll learn how to compress PNG images online using Kix Image Tools, and when lossless versus lossy compression is the right call.
Why PNG files are so large
PNG is a lossless format that uses DEFLATE compression. It preserves every pixel exactly, which is great for sharp text and transparency — but it cannot discard any visual data, so photos saved as PNG can be 5–10× larger than the same image as JPEG or WebP. For simple graphics, the file is also often bloated by an inefficient encoder or an unnecessarily large color palette.
Lossless vs. lossy PNG compression
There are two ways to make a PNG smaller:
- Lossless re-compression (OxiPNG). Re-encodes the DEFLATE stream and optimizes metadata. Pixels are byte-for-byte identical to the original. Expect 5–20% smaller files with zero visual change. This is what Kix Image Tools uses for the PNG output format.
- Lossy PNG (quantization). Reduces the color palette to 256 colors. Files can shrink 60–80%, with mild banding on gradients. Good for flat illustrations, risky for photos.
For most workflows, start with lossless — if the result is still too big, consider converting to WebP or AVIF instead of going lossy on the PNG itself.
Compressing a PNG in Kix Image Tools, step by step
- Open Kix Image Tools in your browser.
- Set Output Format to
PNG. - Drag your PNG files onto the drop zone (batch is supported).
- Wait for the queue to finish — each file shows the original → compressed size and the percentage saved.
- Click Download on a single file, or Download All for the whole batch.
When you should switch formats instead
Compressing the PNG itself has limits. If your image is a photograph, converting to WebP or AVIF at quality 75–80 will usually be 3–5× smaller with no visible difference. Both formats also support alpha transparency, so you don't lose the "no background" benefit of PNG. See our guide to choosing the best web image format for a full comparison.
Tips for the smallest possible PNG
- Reduce the number of colors before exporting (indexed palette instead of RGB).
- Trim invisible padding and crop to the actual content.
- Avoid saving photographs as PNG in the first place — use JPEG/WebP.
- Run files through OxiPNG (or Kix Image Tools) once before publishing; many design tools emit un-optimized PNGs.
Summary
For screenshots and icons, lossless PNG compression with OxiPNG gives you a free size cut with no quality loss. For photos, move to a modern format. Either way, doing it in the browser with Kix Image Tools means it's fast, private, and free.