img-compress

How to Compress Images Without Losing Quality

Big image files slow down websites, blow past email attachment limits, and eat up storage on your phone. The good news: you can usually cut file size dramatically without anyone noticing a difference in quality — you just need to know what you're actually adjusting.

Lossy vs. lossless, in plain terms

Most compression tools work one of two ways:

  • Lossy (JPG, WebP): throws away image detail that's hard for the human eye to notice, in exchange for a much smaller file. This is where most of your savings come from.
  • Lossless (PNG): keeps every pixel exactly as it was, just re-encoded more efficiently. Safer, but the size reduction is much smaller — especially on photos.

If a file needs to shrink a lot, lossy compression is almost always the answer. Lossless is for cases where pixel-perfect accuracy actually matters (a logo, a screenshot with text you need to stay crisp).

The quality slider sweet spot

Lossy compression tools give you a "quality" setting, usually from 1 to 100. Here's the part that surprises people: you don't need it anywhere near 100 for the image to look great.

  • 90–100: visually identical to the original, but you're leaving a lot of easy savings on the table.
  • 70–85: the sweet spot for most photos. The difference from the original is essentially invisible at normal viewing size, but the file can be 50–80% smaller.
  • Below 50: you'll usually start to notice it, especially in areas with fine detail or subtle color gradients (skies, skin tones).

The honest way to find your number: drop the quality to around 80, look at the result at the size it'll actually be displayed at (not zoomed in to 400%), and adjust from there.

A few things that make a bigger difference than people expect

  1. Match the format to the content. A screenshot saved as JPG will look noticeably worse than the same screenshot as PNG or WebP, because JPG isn't built for flat colors and sharp text edges. (We cover this in more detail in WebP vs JPG vs PNG vs AVIF.)
  2. Don't compress an already-compressed file repeatedly. Every lossy re-encode loses a little more detail. If you have the original, compress from that — not from a copy that's already been through the wringer.
  3. Batch similar images with the same settings. If you're processing a set of photos from the same shoot or the same screenshot tool, they'll usually compress well at the same quality setting, which saves you from eyeballing each one individually.
  4. Convert to WebP (or AVIF, where supported) when you can. At the same visual quality, WebP and AVIF files typically come in noticeably smaller than JPG — it's often the single biggest lever you can pull.

Where you compress matters too

A lot of "free image compressor" tools work by uploading your file to a server, compressing it there, and sending it back. That's an extra copy of your image sitting somewhere you don't control, even if briefly.

img-compress does the whole thing — quality adjustment, format conversion, the works — directly in your browser. Your images never leave your device, which matters just as much for a batch of product photos as it does for anything more personal.