JXL stands for JPEG XL. It is an image file that is saved in JPEG XL file format. It supports both lossy as well as lossless compression. JXL is extended version of the JPEG XL file format that was developed by the Joint Photographic Experts Group (JPEG). It can contain an image, illustrations, or screenshot that has been compressed using the JPEG XL compression algorithm.
Brief History of JXL File Format
Aug 2017 - Call for proposals for JPEG XL as next generation image encoding standard
Sep 2018 - Proposals submission
July 2019 - Combination of PIK proposal submitted by Google and FUIF proposal submitted by Cloudinary
Dec 2020 - Informal freezing of bitstream
Oct 2021 - Standardization of the File Format and core coding system
JXL File Format
JXL files are saved as binary files and can be opened in Windows by double clicking the image. The JXL file format provides improved functionality and efficiency as compared to other image file formats such as JPEG, GIF and PNG. The main rivals of JXL file format include AVIF and WebP that both focus on compressing the image size.