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How Image Compression Works: Lossy vs Lossless

D

Dayang

• 5 min read

The Trade-off

Every time you save an image, you are making a choice between Quality and File Size.

Lossless Compression

Lossless compression reduces file size without losing a single pixel of information. It works by identifying statistical redundancies.

  • How it works: Instead of storing "Red pixel, Red pixel, Red pixel", it stores "3 Red pixels".
  • Best for: Logos, diagrams, screenshots with text.
  • Formats: PNG, GIF, WebP (Lossless).

Lossy Compression

Lossy compression aggressively reduces file size by discarding data that the human eye is unlikely to notice.

  • How it works: It simplifies color information. For example, if two pixels are almost the same shade of blue, it might make them the exact same shade to save space.
  • Best for: Photographs, complex artwork.
  • Formats: JPEG, WebP, AVIF.

Which Should You Use?

For the web, Lossy is usually the winner.

A 5MB PNG photo can often be compressed to a 500KB JPEG with barely visible quality loss. That's a 90% savings in bandwidth!

Our Image Compressor tool lets you adjust the quality slider so you can find the perfect balance for your specific needs.