Lossy — it selectively discards visual detail the eye barely notices to dramatically shrink file size. At a high quality setting (around 85%), most photos are visually indistinguishable from the original at a fraction of the size.

WebP typically produces 25–35% smaller files than JPG at the same visual quality, and unlike JPG it also supports transparency (like PNG). For images going on a website viewed in modern browsers, WebP is almost always the best choice.

No. Compression runs entirely in your browser using the Canvas API — your photos never leave your device, which matters when compressing personal photos or documents.

For web images, 75–85% is the sweet spot — big size savings with no visible degradation. Go lower (50–70%) for thumbnails where fine detail doesn't matter, and stay above 90% only if the image will be examined closely or printed.

PNG is already losslessly compressed, and screenshots or graphics with few colors are its ideal case. Re-encoding those as JPG or low-quality WebP can sometimes produce a larger or worse-looking file — for flat-color graphics, keep PNG; for photos, convert to WebP or JPG.