Compress an image

Compression is a trade, so look at both sides of it

Most compressors hide the trade. You upload a file, a number goes down, and you have no idea what happened to the picture until it is printed too small to fix. This page puts the original and the result next to each other at full zoom with a draggable divider, and it prints the estimated output size while you move the slider. You stop where you are comfortable rather than where a website decided for you.

What actually makes a photo heavy

Three things, in order. Pixel count comes first: a 12-megapixel phone photo has around forty times the pixels of a 600 x 600 profile picture, and no amount of clever encoding closes that gap. Detail comes second — grass, hair, textured walls and camera noise all cost bytes, while a plain studio backdrop costs almost none. Encoder quality comes last, and it is the only one the slider touches.

That order explains a common frustration. If a 4 MB photo will not go under 100 KB without turning to mush, the problem is usually the first factor, not the third. Crop the frame down to the head and shoulders and the same 100 KB budget buys a much sharper face.

Quality settings worth knowing

Around 90 the output is visually identical to the original for almost any subject. Between 75 and 85 you are in the sweet spot most websites use: flat areas stay clean and only fine textures soften. Between 60 and 75 edges start to show faint blocks around high-contrast lines such as spectacle frames or text. Below 50 the classic 8-pixel JPEG blocks appear in skies and skin. For a form photograph, aim to stay above 70 and buy the rest of your savings by cropping.

PNG is not a compression setting

People sometimes try to shrink a photograph by saving it as PNG, then wonder why the file grew. PNG is lossless: it promises to reproduce every pixel exactly, so a noisy camera image gives it nothing to work with. PNG earns its place for screenshots of text, line art, logos, and anything with transparency. For faces, JPEG wins every time. This tool will happily read a PNG and give you a JPEG back, which is often the single biggest saving available.

Batch work

Drop a folder and each file is processed with the same settings, listed in a queue with its old and new size. This is the fastest way to prepare a set of scanned documents for an application, or to flatten a directory of product photographs before pushing them to a website. Names are preserved with a suffix so nothing overwrites anything.

Judging quality on the right screen

A phone screen is small, bright and forgiving. Compare the two halves at full zoom, and if the image is destined for print — a photograph on an admit card, a scan a clerk will read — imagine it at that physical size rather than at the size it occupies on your display. Most people stop compressing too late because they judged the result on a screen that flattered it.

Where this tool ends and another begins

Use Crop & rotate when a portal states pixel dimensions. Use Resize to KB when it states a byte window. Use Compress PDF when the file is already a PDF, because compressing the images inside a PDF is a different operation. And if the picture is fine but the form wants a name and date printed across the bottom, the name-and-date tool does that without a photo studio.

Nothing leaves the device

Decoding, drawing and re-encoding all happen through the browser's own image pipeline. There is no server to send bytes to, so there is no retention policy to read and no queue to wait in. It also means the tool is as fast as your device and works with the network switched off once the page has loaded.