What is Image Compression & How Does It Work

Published: March 2025 • 5 min read

How Compression Works

Image compression reduces file size by eliminating redundant data. There are two types: lossy (removes some data permanently) and lossless (preserves all data using smarter encoding).

Lossy Compression

Used by JPG and WebP. Works by: reducing color accuracy in areas the eye cannot easily detect, merging similar adjacent pixels, and using mathematical transforms (DCT) to discard high-frequency detail. At 70-80% quality, the results are visually identical to the original.

Lossless Compression

Used by PNG and GIF. Works by finding patterns in pixel data and encoding them more efficiently. No data is lost, so the image can be perfectly reconstructed. Typical savings: 10-30%.

Try Compression

Our Image Compressor supports both lossy and lossless compression. Try it free.