Compress JPG/JPEG Image Online Free

JPEG compression uses a technique called Discrete Cosine Transform (DCT) that divides the image into 8x8 pixel blocks and converts each block into frequency data. High-frequency detail (sharp edges, fine textures) is discarded first because human vision is less sensitive to it. Low-frequency data (broad colors, gradients) is preserved.

The quality slider controls how aggressively high-frequency data is removed. At 100% nothing is removed. At 50%, significant detail is lost. At 70-80%, the discarded information is in the range human eyes cannot reliably detect — which is why this range is the standard for web and email use.

Archival and print (95-100%): Maximum quality for photos you want to keep indefinitely or print at large sizes. File sizes are large but quality is virtually identical to the original.

Professional web and portfolio (85-90%): Sharp at full size, loads quickly. Standard for photography websites, e-commerce product pages, and anywhere clients or customers scrutinize image quality.

General web and social media (70-80%): The best balance. 75% quality is typically 60-70% smaller than the original with differences that are invisible at normal viewing distances. This is Google's recommended range for web images.

Email and messaging (60-70%): Acceptable quality for images that will be viewed at smaller sizes or low resolution screens. Significant file size savings compared to higher quality settings.

JPG is the right choice for photographs, real-world scenes, and any image with gradients and many colors. It produces the smallest files for photographic content and is universally supported.

PNG is better for screenshots, graphics with text, logos, and anything with sharp edges or transparency. PNG uses lossless compression so it never degrades quality, but files are much larger than JPG for photos.

WebP is the modern web standard — it produces files 25-35% smaller than JPG at the same quality, supports transparency like PNG, and is supported by 97%+ of browsers. If you are optimizing for a website, WebP is the best choice.