Compress PNG Images Online for Free
Reduce PNG file sizes while keeping transparency intact. Adjust quality, preview the result, and download instantly. All processing happens in your browser.
How to Compress a PNG Image
Reducing your PNG file size with ImageSizr.com is quick and easy:
- Upload your PNG file — drag and drop, click browse, paste from clipboard (Ctrl/Cmd+V), import from a URL, or connect Google Drive, Dropbox, or OneDrive.
- Adjust the quality slider — the default is 80%, which works well for most PNG images. Move it lower for smaller files or higher for maximum fidelity.
- Review the preview — check the resulting file size and use the before/after split-view to compare quality.
- Download — click Download to save your compressed PNG.
Use the Calculate Sizes button to compare file sizes at different quality levels before committing to a setting. This helps you find the ideal balance between file size and visual quality.
PNG Compression and Transparency
PNG’s greatest strength is its alpha-channel transparency, and ImageSizr fully preserves it during compression. Transparent areas in your PNG remain transparent in the output.
Use the background toggle to switch between light and dark checkerboard previews. This makes it easy to verify which areas of your image are transparent before downloading.
- PNG output — preserves full transparency and lossless quality.
- WebP output — preserves transparency with even smaller file sizes. A great option for modern web projects.
- JPEG output — does not support transparency. Transparent areas are filled with a background colour (white by default).
Learn more about handling transparency in our guide: preserving transparency when exporting images.
Understanding PNG Compression
PNG uses lossless compression by default, which means no visual data is lost during encoding. The quality slider in ImageSizr controls the compression effort and output encoding to achieve smaller file sizes.
Key things to know about PNG compression:
- Compression only changes file size — your image’s pixel dimensions stay exactly the same.
- Lossless by nature — PNG compression removes redundant data without discarding visual information.
- Best for graphics — PNG excels at screenshots, text-heavy images, logos, and graphics with sharp edges and flat colours.
For the smallest possible PNG files, crop unnecessary areas first before compressing. Removing unused regions reduces the amount of pixel data the encoder needs to process.
When to Use PNG vs Other Formats
Choosing the right format makes a significant difference in file size and quality:
- PNG — use when you need transparency (logos, icons, overlays) or lossless quality (screenshots, text-heavy graphics). Files are larger but pixel-perfect.
- JPEG — use for photos and images where transparency is not needed and smaller file size matters. JPEG is lossy but produces much smaller files.
- WebP — use for the best compression with transparency support. WebP delivers smaller files than both PNG and JPEG while supporting alpha channels.
For format-specific compression, try Compress JPG images or Compress WebP images. For a deeper comparison, read choosing the right quality settings.
Related Tools
- Resize your PNG image — change pixel dimensions to further reduce file size.
- Crop your PNG image — remove unnecessary areas before compressing to reduce pixel count.
- Compress images in any format — use the general compressor for any supported image type.
- Crop tool — crop any image format with the interactive editor.
Read more in our image optimization guides, including how to compress images for faster web pages.
Frequently Asked Questions
How to compress a PNG image?
Upload your PNG to ImageSizr.com, adjust the quality slider (default 80%), review the file size preview and before/after comparison, and click Download to save the compressed image.
Does compressing a PNG remove transparency?
No. PNG and WebP output preserves the full alpha channel. Only JPEG export replaces transparency with a background colour (white by default, or your chosen colour).
How much can I reduce the PNG file size?
It depends on the image content and chosen quality level. Use the Calculate Sizes button to preview file sizes at different quality settings before downloading.
Does compression reduce the image dimensions?
No. Compression only changes the file size by adjusting encoding quality. The pixel dimensions stay the same.
How do I choose the right quality level?
Start at 80% for a good balance of quality and size. Use the before/after split-view preview to compare results visually before downloading.
Is ImageSizr free to use?
Yes. ImageSizr is completely free with no account or sign-up required.
Are my images uploaded to a server?
No. All processing happens directly in your browser. Your images never leave your device, so your data stays private.
What is the maximum file size?
Each file can be up to 10 MB.