How to reduce image size without losing visible quality
Most images are far bigger than they need to be. The three levers that shrink a file, in the order that loses the least and how far each one goes.
A photo straight from a phone is 3 to 5 megabytes and around 4,000 pixels wide. The screen you’re reading this on shows perhaps a quarter of that width and a website, an email or a form needs even less. Most of the file is detail nobody will ever see, which is why it can shrink so much without looking any different.
Lever one: dimensions
Pixel count drives file size more than anything else. Halving the width and height leaves a quarter of the pixels and roughly a quarter of the file and at normal viewing sizes it is invisible. Work out how big the image will actually be shown, allow double for sharp screens and resize to that. For most web and email use, 1,600 to 2,000 pixels on the long side is plenty.
Lever two: quality
JPG and WebP let you trade detail for size. The first steps down from maximum quality remove information your eye doesn’t notice and save a lot; later steps start to show. The image compressor shows the size and a preview as you move the slider, so you can stop at the point where the picture still looks right. Around 75 to 85 is the usual sweet spot for photos.
If you need a specific number, such as an upload form’s limit, the size pages search for the best quality under a target: under 100KB or under 500KB, for example.
Lever three: format
The same photo saved as WebP is typically a quarter to a third smaller than as JPG at similar quality. For your own website, PNG to WebP or converting JPGs to WebP is one of the easiest wins available. For screenshots and graphics, PNG often beats JPG and which image format should I use covers the choice.
The order matters
Resize first, then compress, from the original each time. Compressing a large image and then shrinking it throws away detail twice. Compressing an already-compressed JPG stacks the losses. If a single photo is the problem, your photo is too large to email walks through the one-pass version.
What not to do
Don’t rely on renaming or zipping. Changing the extension doesn’t change the file and zipping a JPG saves almost nothing because it is already compressed.
For a related next step see Why won’t a website accept my photo?.
Common questions
Can I make a file smaller with no loss at all?
A little. Removing metadata saves a few kilobytes to a few hundred and a lossless re-save of a PNG can trim more. Big reductions always involve throwing away something, but done in the right order, nothing you can see.
What quality setting should I use?
Around 75 to 85 for photos. Above 90 the file grows quickly for differences almost nobody can see. Below 60 artefacts start to show around edges and in skies.
Why did my PNG get bigger when I converted it to JPG?
It usually gets smaller, but a PNG of a flat graphic with few colours can already be tiny and JPG handles that kind of image badly. Keep graphics, logos and screenshots as PNG or try WebP.
Does compressing the same image twice make it worse?
Yes, each JPG save loses a little more. Always compress from the original, not from a previously compressed copy.