How JPEG Compression Works

JPEG (Joint Photographic Experts Group) uses lossy compression based on the Discrete Cosine Transform (DCT). When you reduce the quality factor, the encoder discards high-frequency detail that the human eye is less sensitive to. Our tool runs a binary search across quality values 10–95 to find the highest quality that still fits inside your target size.

Lossy vs lossless

True lossless JPEG re-encoding is rare. Our compressor uses smart lossy optimization that preserves perceived quality while dramatically shrinking file size — typically 60–90% reduction.