JPG Image Compressor Online

JPEG uses lossy compression based on the Discrete Cosine Transform (DCT). It converts pixel color values into frequency coefficients and applies quantization matrices to discard high-frequency visual data that the human eye is least sensitive to. By adjusting the quality slider, you control the aggressiveness of this quantization, balancing file size against photographic sharpness.

For websites and digital sharing, a quality setting between 75% and 82% offers the ideal balance. At this range, JPEG images typically achieve a 65–80% reduction in file size compared to uncompressed photos while visual compression artifacts remain virtually imperceptible.

Yes. Switch to Target Size mode in InImageCompressor and enter your desired file size in KB. Our 7-pass binary search algorithm tests quantization levels in your browser to find the highest possible quality that fits within your exact KB limit.

No. The JPEG specification does not support an alpha transparency channel. If you upload an image with a transparent background and compress it as JPEG, the transparent areas will automatically be filled with a solid background (white by default). If you need to preserve transparency, select WebP or PNG as your output format.

Caesium is a respected open-source desktop image compressor for Windows and Mac. While Caesium requires downloading, installing, and updating software on your local machine, InImageCompressor provides equivalent lossy compression algorithms directly in your browser without any installation, working across all operating systems and mobile devices while still processing files 100% locally on your device.

If your target audience uses modern browsers, converting JPG to WebP can yield an additional 25–35% file size savings at the same visual quality. InImageCompressor allows you to convert between JPG, WebP, and AVIF with a single click in the Settings panel.