PNG to JXL Converter

Encoding: the PNG uses lossless DEFLATE with a prediction filter chosen per row; JXL uses lossy VarDCT or lossless modular coding; existing JPEGs can be repacked without loss, and the download is a JPEG XL encoded with libjxl compiled to WebAssembly, lossy at the quality you choose or lossless.

Bit depth: 1, 2, 4, 8 or 16 bits per channel in the PNG; JXL allows 8 to 16 bits per channel, or floating point, and the JXL written here has 8 bits per channel. 16-bit PNGs from photo and scientific software are reduced to 8 bits per channel.

Colour: RGB, greyscale, or an indexed palette of up to 256 colours in the PNG; JXL supports sRGB, Display P3, linear and other spaces described in the codestream, written here as 8-bit sRGB.

Transparency: the PNG stores it as a full alpha channel, so edges and shadows can fade smoothly; the JXL keeps it as an extra channel in the codestream.

Metadata: the PNG can carry text chunks, an ICC profile, physical resolution and EXIF in an eXIf chunk; JXL can carry EXIF and XMP boxes in the container form, often stripped by encoders, but nothing is copied across.

PNG stores pixels losslessly with full alpha transparency. It is ideal for screenshots, logos, UI and anything with sharp edges, but photos saved as PNG are several times larger than JPEG.

A PNG opens with an 8-byte signature and is a chain of chunks, each with its own CRC: IHDR (size, depth, colour type), optional PLTE and tRNS for palettes, one or more IDAT chunks with the compressed rows, and IEND.

PNG files usually come from screenshots, design exports, logos and web graphics.

JPEG XL is a next-generation format designed to replace JPEG. It compresses better than JPEG and WebP, supports lossless, HDR and progressive decoding, and can losslessly repack existing JPEGs.

A JPEG XL file is either a bare codestream starting with FF 0A or an ISO base media container whose 'jxlc' box holds the codestream. A recompressed JPEG keeps a 'jbrd' box that lets the original JPEG bytes be rebuilt exactly.

JXL is the better choice for archiving and future-proof high quality storage, while PNG suits screenshots, logos, graphics and anything that needs transparency.

JXL strengths: Excellent lossy and lossless compression; Progressive decoding and HDR; Huge image sizes. Drawbacks to weigh: Browser support is limited (Safari only by default); Few apps can open it yet.