JPEG XL

File Format
Name	JPEG XL
Ontology	Electronic File Formats Graphics JPEG XL
Extension(s)	.jxl
MIME Type(s)	image/jxl
PRONOM	fmt/1484, fmt/1485
Extended From	[[JPEG, PIK, FUIF]]
Magic Bytes	FF 0A or 00 00 00 0C 4A 58 4C 20 0D 0A 87 0A
Patent License	Royalty-Free
Released	2021

JPEG XL is a compressed image format and/or file format that is yet another attempt to be the next JPEG. It was first announced around 2017-08. It is expected to be published as ISO/IEC 18181.

JPEG XL is based in part on the FUIF and PIK formats.[1] The standard also supports recompression of JPEG files with bit-exact reconstruction.

Identification

• Based on the reference implementation, JPEG XL codestreams start with bytes ff 0a.
• Codestreams may also be wrapped in an ISOBMFF-based file format (implementation). See format overview:
  • the first 4 bytes would be the size of the box (00 00 00 0C, meaning 12 bytes long),
  • the box ID would be 4A 58 4C 20 (in ASCII JXL ) and
  • the box content would be the overall signature 0D 0A 87 0A.

Specifications

• Committee Draft of JPEG XL (2019-08)
• ISO/IEC 18181

Libraries

• libjxl - official libjxl implementation in C++
• JPEG XL Library for Delphi/Lazarus/FreePascal - simple open source library

Software

• Open-source reference software
• Online converter to JXL
• GIMP Support
• jxl2png - Simple command line converter to PNG/BMP/JPG/PNM

Sample files

• dexvert samples — image/jpegXL

Links

• Overview of JPEG XL
• Next-Generation Image Compression (JPEG XL) Draft Call for Proposals (2017-11)
• Revised Draft Call for Proposals (2018-02)
• Final Call for Proposals (2018-04)
• Gigazine article (2017-08-15)
• Slides from Imagecon 2019 presentation
• Introductory paper (open access)
• Benchmarking JPEG XL image compression
• How JPEG XL Compares to Other Image Codecs (2020-05-26)
• Codestream vs Container discussion