PNG

Yes, specifically for graphics, screenshots, logos, and anything requiring transparency or exact lossless fidelity. It is not the standard choice for archiving photographic scans, where TIFF and JPEG 2000 dominate because of broader bit-depth, CMYK, and multi-page support.

PNG exists because of a licensing dispute, not a technical shortfall: in late 1994 Unisys announced it would enforce its patent on the LZW compression used inside GIF, prompting the independent PNG Development Group to design a royalty-free, unpatented DEFLATE-based lossless replacement.

Yes. PNG's alpha channel supports a full 8-bit range — 256 levels of partial transparency per pixel — rather than the binary on/off masking GIF uses. Combined with indexed, grayscale, or truecolor modes up to 16 bits per channel, PNG can represent up to 64 bits per pixel including alpha. That granularity is what lets soft edges, drop shadows, and semi-transparent overlays render cleanly instead of the jagged, single-color fringing GIF transparency produces.

It can, via the eXIf chunk, but that was only added to the core W3C spec in the Third Edition in June 2025. Many export pipelines — browsers, screenshot tools, older editors — still omit embedded metadata by default.

Even though the PNG spec supports XMP (iTXt chunks) and now a formal EXIF chunk, most PNG-producing tools don't embed it by default, so PNG assets frequently depend more on manual tagging or filename-based ingest rules than on embedded metadata extraction.

Yes. PNG uses lossless DEFLATE compression, so re-saving a PNG never discards pixel data the way JPEG's lossy re-encoding does with each pass. Open, edit, and save a PNG a hundred times and — provided the underlying pixel content is unchanged — the decompressed image data comes back byte-identical to the original every time. That makes PNG a safe intermediate or working format for multi-step editing pipelines, unlike JPEG, where repeated open-edit-save cycles compound generation loss with each save.

PNG uses DEFLATE, the same lossless compression algorithm behind ZIP archives and gzip. DEFLATE combines LZ77 dictionary-based redundancy elimination with Huffman entropy coding to shrink file size without discarding any pixel data — decompression reconstructs the image pixel-for-pixel identical to the source. DEFLATE was deliberately chosen because it was unencumbered by patents, unlike GIF's LZW, whose Unisys patent enforcement in 1994 was the direct reason PNG was created in the first place.

PNG supports several metadata channels: tEXt and iTXt chunks hold arbitrary key-value text pairs (including embedded XMP packets), iCCP chunks carry ICC color profiles, and — since the Third Edition became a W3C Recommendation in June 2025 — a dedicated eXIf chunk carries native EXIF data, which previously had to be wrapped inside XMP. In practice, though, most PNG-producing tools (browsers, screenshot utilities, many editors) still don't populate these chunks by default, so PNGs often arrive with no embedded metadata at all.