PNG to JPG

PNG's lossless compression preserves every pixel exactly, which is great for screenshots and graphics but produces large files for photographic content because it can't discard the subtle gradients and noise that make up most of a photo's data. Converting to JPG applies lossy DCT compression and chroma subsampling instead, which throws away detail the eye is least sensitive to and typically cuts file size dramatically for photo-like images — often to a fraction of the original PNG.

This conversion is the usual fix for oversized PNG photos: screenshots saved as PNG by default, photos exported from design software in PNG format, or images downloaded from a source that only offers PNG. Shrinking them to JPG makes uploads faster, keeps pages under file size limits, and reduces storage and bandwidth use, at the cost of some fine detail depending on the quality setting used.

The one thing this conversion cannot carry over is transparency, since JPG has no alpha channel at all. Any transparent or semi-transparent pixels in the source PNG are flattened onto a solid background before encoding, so this conversion isn't appropriate for logos, icons or graphics that rely on a transparent background — those should stay in PNG or move to WEBP instead.