Lossy and Lossless Compression: What You Lose and What You Keep

To make a photo smaller, software compresses it. There are two broad approaches, and knowing which is which helps you keep quality where it matters.

Lossless compression

Lossless compression shrinks a file without discarding any information. When you open it, every pixel is exactly as before, much like a zip file.

• Examples: PNG, and lossless modes of WebP.
• Result: moderate size savings.
• Best for: screenshots, logos, text-heavy images, and images you'll edit again.

Lossy compression

Lossy compression permanently throws away detail the eye is unlikely to notice, such as tiny colour differences.

• Examples: JPEG, and lossy WebP.
• Result: much smaller files.
• Best for: photographs.

The quality setting

Lossy formats let you choose a quality level. Lower quality means a smaller file and more visible loss.

Quality setting	Typical result
High (about 85–95%)	very close to the original
Medium (about 70–85%)	good for sharing; small visible loss
Low (below about 60%)	obvious blockiness, banding or blur

For most everyday sharing, a medium setting saves a lot of space without visible harm.

The trap of repeated saving

Each time you re-save a JPEG, the compression runs again and a little more detail is lost. After many rounds, artifacts pile up.

1. Keep the original.
2. Compress once, from the original, to the size you need.
3. Don't re-compress an already compressed copy unless you must.

Which to choose?

If you have	Choose
A photograph to share or upload	lossy, at medium-high quality
A screenshot with text	lossless
A logo or graphic with flat colour	lossless
A file you'll keep editing	keep the original lossless or high quality

Adjustable quality

A compression tool with an adjustable quality slider lets you find the smallest size that still looks good to you. Try a medium value first and compare.

Try Image Compress & Resize Tool →