Compress an Image

Lossy compression works by throwing away detail your eye is least likely to miss: fine texture in busy areas, subtle color variations, and high-frequency noise. A quality setting of 80 to 85 is the sweet spot for photographs - most people cannot tell it apart from the original at normal viewing size, yet the file often lands at a quarter of its starting weight. Below about 60, block artifacts start creeping into smooth gradients like skies and skin.

This tool uses the encoders your browser already ships with, driven through the Canvas API. That has two practical consequences. First, there is nothing to install and no queue to wait in - encoding a 12-megapixel photo takes well under a second on a typical laptop. Second, results can differ by a few percent between Chrome, Firefox and Safari, because each vendor tunes its JPEG and WebP encoders differently.

Format choice matters as much as the quality slider. At comparable visual quality, WebP files come out roughly 25 to 34 percent smaller than JPEG, and every current browser can display them. If your image has large flat areas, sharp text or transparency, PNG or WebP will treat it far better than JPEG, which smears hard edges with ringing artifacts.

When the slider alone will not get you small enough, reduce the pixel dimensions before compressing. A 4000-pixel-wide photo destined for a web page that renders it at 800 pixels carries 25 times more pixel data than needed; downscaling first shrinks the file more than any quality setting can, and it removes the sensor noise that makes JPEGs hard to compress in the first place.