Will optimizing reduce my image quality?
1 min read · Last updated June 2026
For normal use, no. SlashImage shrinks the file without any change you can see - the result looks the same to the eye, even though it is not a byte-for-byte copy of what you uploaded.
Visually identical, not pixel-identical
Most optimization is "visually lossless." SlashImage removes detail your eye cannot pick out anyway - tiny variations in areas that look flat, noise you would never notice - so the picture looks the same while the file gets much smaller. It is not pixel-for-pixel identical to your upload, but on a screen you cannot tell the difference.
Your colors stay accurate, too: SlashImage always keeps each image's color profile (its ICC profile), so nothing shifts or washes out.
The compression mode setting
For more control, the Compression section of the settings has a Compression mode with three choices:
- Lossy (the recommended default) - the smallest files, with quality differences invisible to most viewers. Right for almost every site.
- Glossy - higher quality with a bit less compression. A good pick for photography or portfolio sites where fidelity matters most.
- Lossless - keeps every pixel exactly as it was, but saves the least space. Choose this only when you need pixel-perfect images.
Most sites should leave it on Lossy.
Your original is always safe
Whatever mode you choose, SlashImage keeps a backup of your untouched original, so you can restore it at any time if you change your mind.