Compress your images without leaving your device

Choose the format before you touch the slider

Format decides more about the final size than the quality setting does. JPG is the safe default for photographs and the one thing every piece of software on earth can open. WebP usually lands 25-35% below a JPG of comparable quality, and it works everywhere that matters now. AVIF goes further still — often around half the size of the JPG — at the cost of slower encoding. PNG is the odd one out: it's lossless, which makes it right for screenshots, logos, line art and anything that needs transparency, and wrong for photographs.

So: publishing to the web and not worried about ancient browsers, use AVIF or WebP. Sending the file into an email, a government upload form or somebody else's software, use JPG. Transparent background that has to survive, use PNG or WebP — JPG will fill it with white.

What the quality slider actually does

It sets the encoder's quality parameter directly: 80 here is 80 in the encoder, not a marketing scale. That number is not a percentage of visual fidelity, though, and the relationship is steeply non-linear. Going from 100 to 90 often halves the file with nothing visible lost, while going from 50 to 40 saves comparatively little and starts smearing detail you will notice.

For photographs, 75-85 is the range where almost nobody can tell the difference at normal viewing size. Below 60 you'll start seeing blocking in skies and gradients — smooth areas are where lossy compression fails first and most obviously. Above 90 you're mostly spending bytes on detail no one is going to look at.

It won't change the dimensions

This tool re-encodes; it doesn't resize. A 4000×3000 photo goes in and comes out 4000×3000, just lighter. That's deliberate — how small an image should be depends entirely on where it's going, and quietly deciding that for you would be the wrong default.

Worth knowing, because resizing is usually the bigger lever of the two. If a 4000px-wide photo is headed for a blog post that displays it at 800px, scaling it down first beats any quality setting you could pick. Compress after resizing, not instead of it.

When compression won't get you much

A JPG that has already been compressed once has had that detail thrown away for good; running it through again at high quality mostly re-encodes the artifacts it already has. If a file barely shrinks, that is usually why — and it's a sign to leave it alone rather than drag the slider down until something gives.

PNG to PNG is the other case. PNG is lossless, so the quality slider has very little to work with there; the savings come from converting to a lossy format instead. And text-heavy screenshots compress badly as JPG — the hard edges of letters are exactly what lossy encoders smear. Keep those as PNG or WebP.

Doing it in bulk

All of the above applies the same to 200 files as to one. Select a whole folder, set the format and quality once, and take the result as a single ZIP. Because the work happens on your own machine, what limits you is your CPU and how much memory the browser gives a single tab — not a queue, a daily allowance or an upload speed. A big batch is a good moment to leave the tab open and go do something else.