FileGizmo glossary
Lossy vs lossless
Lossy compression shrinks a file by permanently discarding detail your eye is unlikely to miss, which is how JPG makes small photos. Lossless compression shrinks a file while keeping every original pixel, which is how PNG works. Lossy gives smaller files, lossless keeps perfect quality.
Why the difference matters
When you shrink an image you are making a choice, even if a tool hides it. Lossy compression buys a small file by throwing away detail for good. Lossless compression keeps every pixel but cannot shrink nearly as far. Neither is better in the abstract. The right one depends on the job.
A holiday photo for a website wants lossy, because nobody will notice the discarded detail and the smaller file loads faster. A logo, a screenshot, or a scan with sharp text wants lossless, because lossy compression smears fine edges and makes text look muddy.
How to control it
- Open the image compressor and watch how quality settings trade size against detail.
- To switch between a lossy format like JPG and a lossless one like PNG, use the image converter.
- Always compress from an original rather than a file you already shrank once.
Both tools run in your browser, so the images stay on your device while you experiment.
Frequently asked questions
Is JPG lossy or lossless?
JPG is lossy. Each time you save a JPG it discards some detail, and repeated re-saving slowly degrades the image. PNG is lossless and keeps every pixel, which is why it suits graphics and screenshots.
When should I use lossy compression?
Use it for photographs headed to the web or email, where a much smaller file matters more than perfect detail. The quality loss is usually invisible at sensible settings.
Does compressing an image twice make it worse?
With lossy formats, yes. Every lossy save throws away a little more detail. Keep an original and compress from it once rather than re-compressing an already compressed file.