How lossless compression works
Lossless methods look for repetition. Long runs of similar pixels, flat backgrounds, and repeated color values are replaced with a compact description that a decoder expands back into the exact original.
Because nothing is discarded, a file can be compressed, decompressed, and recompressed indefinitely without any drift in quality. That property makes lossless formats safe for masters and edits.
Formats that compress losslessly
PNG is the everyday example for images, while GIF, BMP, and typical TIFF files also avoid pixel loss. ZIP applies the same idea to any file, including photographs that are already compressed.
The limit is simple: files with little internal pattern do not shrink much. A detailed photograph gives a lossless compressor very little redundancy, so savings are modest compared with lossy encoding.
- PNG for graphics, screenshots, and transparency
- TIFF for scanning, print, and archival masters
- GIF for flat-color graphics within its palette
- ZIP for packaging files without altering their contents
When lossless is worth the size
Choose lossless whenever re-decoding must be exact: text-heavy screenshots, diagrams, logos, medical or legal imagery, and files that will be edited again later.
Filekind converts lossless PNG files to JPEG when a smaller photograph-style file is needed. Converting to JPEG is a lossy step, and transparent areas become white, so keep a PNG master if pixels must stay exact. PNG input can also become static WebP, which keeps transparency while usually cutting the size further.