Image compression vs resizing: what's the difference?

People use "compress" and "resize" interchangeably — but they're different operations with different outcomes. Understanding the difference saves you file size and quality.

The difference

• Compressing — keeps dimensions, reduces file size by removing detail (lossy) or optimizing encoding (lossless)
• Resizing — changes pixel dimensions; a 4000px photo becomes 1000px, which inherently shrinks the file

Which to do first

Resize first, then compress. Resizing to the target dimensions (e.g. 1080px wide for web) usually removes 70-90% of the file size alone. Compressing after that trims the rest.

How to do it

1. Resize to your target dimensions
2. Compress the result at quality 75-80

When to skip resizing

If you need the full resolution (printing, archival), just compress — quality 80-85 is visually lossless for most photos.