PNG Compression: How to Reduce PNG File Size

PNG files are often much larger than they need to be. A 5 MB PNG screenshot can easily become 500 KB without visible quality loss. Here is how PNG compression works and how to get the smallest possible files.

How PNG compression works

PNG uses a two-step process: filtering and DEFLATE compression. The filter step rearranges pixel data to make it more compressible. The DEFLATE step (the same algorithm used in ZIP files) compresses the filtered data.

This is all lossless — not a single pixel changes. The compression ratio depends on the image content. Simple images with large flat-color areas compress well. Photos with complex textures and gradients compress poorly.

Two approaches: lossless and lossy

Lossless PNG compression

Lossless compression optimizes the encoding without changing pixel data. Typical savings: 10-30%. This is safe for any use case because the output is pixel-identical to the input.

Tools like OptiPNG, Zopfli, and OxiPNG try different filter strategies and compression parameters to find the smallest possible encoding. This takes time (especially Zopfli) but the results are guaranteed lossless.

Lossy PNG compression

Lossy PNG compression reduces the number of colors in the image. A full-color PNG (PNG-24) with millions of colors can be converted to a 256-color PNG (PNG-8) with dramatically smaller file sizes — typically 60-80% smaller.

The tool pngquant is the best at this. It uses a sophisticated algorithm to choose the best 256 colors and applies dithering to simulate gradients. For many images — logos, icons, UI elements — the visual difference is imperceptible.

PNG-8 vs PNG-24: when 256 colors is enough

PNG-24 stores each pixel with 24 bits (16.7 million colors). PNG-8 uses an 8-bit palette (256 colors). The file size difference is dramatic:

For logos, icons, and flat illustrations, PNG-8 saves 70-80% with no visible quality loss. For photos, 256 colors is not enough — you will see banding in gradients and color shifts.

When to convert PNG to another format

Sometimes the best PNG compression strategy is to not use PNG at all.

Photos in PNG: Convert to JPEG. A 5 MB PNG photo becomes a 400 KB JPEG at quality 0.85 with no visible difference. Use MiniPx's PNG to JPG converter.

Web graphics: Convert to WebP. WebP supports transparency (like PNG) but compresses much better — typically 30-50% smaller files. Use PNG to WebP conversion.

Keep as PNG: When you need pixel-perfect accuracy (technical diagrams, text-heavy images), when transparency is required and WebP is not supported, or when the file will be edited further (PNG is a better editing format than JPEG because of no generation loss).

Compressing PNG with MiniPx

Open MiniPx PNG Compressor and upload your PNG file. For photos, select JPEG as the output format — this gives the biggest size reduction. For graphics that need transparency, stay with PNG and use the Tiny preset.

MiniPx can also resize your PNG during compression. If your 3000 x 2000 pixel screenshot only needs to be 1200 pixels wide, resizing during compression combines both optimizations in one step.

Tips for creating smaller PNGs

Use fewer colors. Flat-color designs compress dramatically better than gradients. If you are designing icons or UI elements, use solid colors where possible.

Reduce dimensions. A 2x resolution icon at 512 x 512 pixels is 4 times the pixel data of a 256 x 256 version. Export at the exact dimensions you need.

Avoid unnecessary transparency. If your image does not need transparency, save it without an alpha channel. This removes 8 bits per pixel from the file.

Frequently asked questions

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