How to Compress PNG Without Losing Quality

PNG was designed to be a lossless format — it stores image data without discarding any information. This makes PNG ideal for quality-sensitive work, but it also means PNG files are large. The good news: there are several ways to compress PNG without losing quality, and the results can be dramatic.

Understanding lossless PNG compression

True lossless PNG compression re-encodes the same pixel data using more efficient algorithms without changing a single pixel value. The output looks absolutely identical to the input — because it is mathematically identical. Differences exist only in how the file stores the data internally.

Standard PNG encoders are not always optimal. When you save a PNG from Photoshop, GIMP, or a mobile device, the encoder may not use the most efficient compression settings. Running the PNG through a dedicated optimizer can achieve 5–30% reduction without any quality change.

The most effective method: convert to WebP

If you need to deliver images on the web and want to compress PNG without losing quality, converting to WebP is the highest-impact approach:

• WebP uses more sophisticated compression algorithms than PNG.
• WebP lossless mode typically produces files 25–35% smaller than equivalent PNG files.
• WebP is supported in all modern browsers (Chrome, Firefox, Safari, Edge).
• WebP supports transparency (like PNG) so you don't lose alpha channel support.

This means you can serve the same visual quality at significantly smaller file sizes — which is better than any PNG compressor can achieve with lossless output.

Step-by-step: compress PNG without losing quality using Resizo

• Step 1: Open Resizo in your browser.
• Step 2: Drop your PNG file onto the tool.
• Step 3: Keep the original dimensions (do not resize if you need exact pixel dimensions).
• Step 4: Select WebP as output format for lossless-equivalent compression.
• Step 5: Download the result and compare file sizes. You should see 25–35% reduction.

When you specifically need PNG output

Some workflows require PNG output specifically — design files, print production, systems that don't support WebP, or files that will be edited further. In those cases:

• Remove unnecessary metadata: PNG files often contain embedded metadata (GPS data, camera settings, color profiles) that is irrelevant for web display. Stripping this can save 5–15% without touching pixel data.
• Reduce color depth: If your PNG has 16 million colors but uses only 256, switching to 8-bit indexed color reduces file size dramatically. This works for logos, icons, and illustrations — not photographs.
• Use lossless re-encoding: Tools like pngcrush and zopflipng find more efficient internal encodings for the same data.

Common mistakes when compressing PNG

Using JPG for quality-sensitive PNG content: JPG is lossy and will introduce artifacts on images with sharp edges, text, and solid colors. Never convert a logo or UI graphic to JPG thinking it will maintain quality — it won't.

Excessive resizing: Reducing dimensions beyond what's needed for display loses actual content. Resize to the exact display dimensions, no smaller.

Repeated compression: Running a PNG through compression tools multiple times does not give compounding savings. The first pass captures all available lossless optimization. Subsequent passes yield negligible gains.