Lossy compression reduces file size by permanently discarding data deemed less perceptible, trading some quality for significantly smaller files.
Lossy compression is a data encoding method that reduces file size by permanently removing information considered less important or less perceptible to human senses. In images, this means discarding fine color gradients and high-frequency detail; in audio, it means removing frequencies outside typical human hearing range. The key advantage is dramatically smaller files — a JPG can be 10-20x smaller than the equivalent uncompressed image with minimal visible quality loss. The trade-off is that each re-save degrades quality further (generation loss), and the discarded data cannot be recovered. Common lossy formats include JPG, MP3, AAC, and H.264 video.
Lossless compression reduces file size without discarding any data, allowing the original file to be perfectly reconstructed from the compressed version.
A codec (coder-decoder) is an algorithm that compresses and decompresses audio or video data, determining the quality, file size, and compatibility of media files.
Bit depth determines how many distinct colors or tones each pixel (or audio sample) can represent, directly affecting quality and file size.
WebP is a modern image format developed by Google that provides superior lossy and lossless compression for images on the web.