PNG uses lossless compression and supports full alpha transparency, making it suitable for screenshots, icons, line art, text, and compositing assets with clean edges. It preserves the re-encoded pixels exactly but is commonly larger than JPG or WebP for photographs.
The converter re-encodes a readable source as a static PNG in the browser. Moving to a lossless format does not restore detail already removed from a JPG; it only avoids new lossy degradation in the PNG save. Animation, original color profiles, and some metadata may not carry over.