What is lossy compression?
Definition
Lossy compression makes an image file much smaller by permanently discarding some of its data, usually fine detail and subtle color changes. JPEG is the best known lossy format. The lost detail cannot be restored afterward.
Why it matters for sellers
For most product photos, lossy compression is the practical choice. At a sensible quality setting a listing photo looks the same at normal viewing size, while the file loads much faster.
Pushed too far, it causes visible blocks, smeared texture and halos near edges, which can make fabric, jewelry or text look cheap. Because the damage is permanent and builds with each re-save, sellers should compress a copy and keep the original.
How to do it with Instasize
The Instasize Image Compressor lets you control the trade-off. You set a target size or quality, then compare against the original.
- Upload your JPG, PNG or WebP image.
- Choose a target file size or move the quality slider.
- Check the result at full size for blocky edges or smeared texture.
- Raise the quality if you see damage, then download.
Related Instasize pages
Examples
Gallery of knitwear photos
A seller compresses sweater photos to a lighter size. Wool texture stays visible at normal size and the product page loads faster.
Over-compressed jewelry
A ring photo compressed too hard shows smeared metal and speckled edges. Raising the quality setting restores a clean look.
Screenshot with text
A screenshot saved as a lossy file shows noise around the letters, so a lossless format works better.
Frequently asked questions
Can I undo lossy compression?
No. The discarded detail is gone. That is why you should keep the original file and work on copies.
What quality setting should I use?
There is no single right value. Lower it until you notice damage at full size, then go a little higher.
Which formats use lossy compression?
JPEG is always lossy. WebP can be lossy or lossless. PNG is lossless.
Does saving a lossy file twice hurt it?
Yes, it often does. Each save can discard more detail, so avoid repeated re-saving.