How to compress images without losing visible quality

"Compress" sounds like it always costs you quality. In practice, most photos carry far more data than the eye can use — so you can often cut the file size dramatically before anyone notices a difference.

Lossy vs. lossless, in one sentence

Lossless compression rearranges data more efficiently but keeps every pixel identical — smaller file, zero quality change, but limited savings. Lossy compression selectively discards detail the eye barely registers — much bigger savings, with a quality dial you control. For photographs, lossy (JPG, WebP, AVIF) is almost always the right choice.

Where the savings actually come from

Two very different things get lumped together as "compressing an image," and knowing which one you need matters:

1. Resizing — reducing pixel dimensions. If your image displays at 800px wide, a 4000px original is carrying 5x more data than needed, before compression even starts. This is usually the biggest single saving.
2. Re-encoding — lowering the quality setting within the same dimensions. This is the classic "quality slider" and is where diminishing returns kick in.

Do both: resize to the size you'll actually display, then compress. Doing only one leaves savings on the table.

Finding the quality sweet spot

Image quality vs. file size isn't linear — there's a point where dropping quality a little more saves almost nothing, and a point below that where artefacts suddenly become visible (blocky patches, colour banding). A good rule of thumb: start around 75–80% quality for JPG/WebP and only go lower if the size still isn't small enough. Most people can't tell 80% from 100% on a photo; almost everyone can tell 40% from 100%.

Hitting an exact target size

Sometimes you don't want "smaller" — you want "under 50KB" for a specific upload limit. Rather than guessing a quality percentage, a target-size tool searches for the highest quality that still fits your limit, resizing further only if needed. That gets you the best possible result within the constraint, not just a rough guess. Our Image Size Reducer does exactly this — pick "under 50KB" and it finds the best quality/size combination automatically.

A quick checklist

• Resize to display size first.
• Use a modern format (WebP or AVIF) if the destination supports it.
• Start compression around 75–80% quality.
• Zoom in at 100% before publishing to check for visible artefacts.