Lossless image compression

Reduce file size without losing a single pixel. Lossless compression preserves exact image quality while optimizing file size.

✨

Open Lossless Compressor →

PNG format with Gentle preset for lossless optimization

Lossless Image Compression | MiniPx — Free, Fast & Private

Lossless compression reduces file size without discarding any image data. Every pixel in the output is identical to the original. This is essential for medical imaging, technical diagrams, screenshots with text, and any image where pixel-perfect accuracy matters.

PNG is the primary lossless format for web use. MiniPx optimizes PNG files by improving the compression algorithm efficiency — reorganizing data to compress better without changing a single pixel value.

The trade-off is that lossless compression achieves smaller reductions than lossy compression. While lossy JPEG compression might reduce a photo by 80-90%, lossless PNG optimization typically achieves 10-30% reduction. The benefit is zero quality loss.

For photographs where minor quality loss is acceptable, lossy formats (JPEG, WebP) produce dramatically smaller files. Lossless compression is best reserved for graphics, screenshots, diagrams, and images that will be edited further.

MiniPx processes lossless compression entirely in your browser. No images are uploaded to any server — important when working with sensitive technical documents and medical images.

How it works

Upload your image: Add the image you want to compress losslessly. PNG format works best for lossless optimization.
Select PNG format: Choose PNG as the output format. PNG uses lossless compression by design.
Use Gentle preset: Gentle applies minimal processing — no lossy compression, just optimization of the PNG encoding.
Download optimized image: The output is pixel-identical to the input, just in a smaller file.

Frequently asked questions

What is lossless compression?

Lossless compression reduces file size without removing any image data. The decompressed image is pixel-for-pixel identical to the original. PNG and WebP (lossless mode) support this.

How much can lossless compression reduce file size?

Typically 10-30% for PNG files. The reduction depends on image content — screenshots and diagrams with large flat-color areas compress well, while photographs see smaller reductions.

When should I use lossless vs lossy compression?

Use lossless for medical images, technical diagrams, screenshots with text, images for further editing, and any case where pixel accuracy matters. Use lossy for photographs, web images, and social media where file size matters more than pixel-perfect accuracy.

Is PNG always lossless?

Yes. PNG format uses lossless compression by design. Every PNG file preserves exact pixel values. However, converting from JPEG to PNG does not recover quality lost during JPEG compression.

Can I losslessly compress JPEG files?

JPEG format is inherently lossy. You can optimize JPEG encoding efficiency, but some data has already been discarded during the initial JPEG compression. For truly lossless storage, use PNG or TIFF.

Does MiniPx support WebP lossless?

MiniPx primarily optimizes through format conversion and compression presets. For guaranteed lossless output, use PNG format which is lossless by specification.