A few notes
Why does compression happen in the browser?
No upload means no privacy worry, no size limit from a file host, and instant feedback. It also makes batch compression so affordable that you can process a whole folder in one drag-and-drop.
What affects how much I can save?
Photos compress a lot (often 60โ80% at quality 80). Screenshots and graphics compress less. The two biggest levers here are the quality slider and converting photos to WebP, which usually beats JPEG at the same visual quality.
Is WebP supported everywhere?
All modern browsers read WebP, including Chrome, Edge, Firefox and Safari 14+. For older setups the JPEG or PNG output is always available as a fallback.
Will compression hurt my image quality?
At quality 80โ90 the difference is usually invisible to the eye but the file is far smaller. Lower the number only when you need maximum compression for web delivery.