pngcrush vs XConvert Image Compressor

pngcrush is a free command-line utility for losslessly optimizing PNG files. It tries compression levels and PNG filter methods to reduce the size of a file’s IDAT datastream, and supports batch processing. Its chunk controls can remove unwanted ancillary chunks or add gAMA, tRNS, iCCP, and textual chunks. The supported format is PNG; image resizing and API access are not provided. pngcrush runs from MSDOS, UNIX, or Linux command lines, and the maker links to precompiled Windows binaries for an MSDOS window. Source code is available from SourceForge and the pmt git repository, with libpng and zlib included in the distribution. The maker permits use, modification, and redistribution without a fee; the license is equivalent to, but not identical with, the libpng license. Build choices matter: the maker warns about overflow vulnerabilities when compiling with certain older unpatched libpng versions, and says a build statically linked with the supplied zlib is believed to avoid a particular double-free bug. The SourceForge files page lists pngcrush-1.8.11.tar.xz as the latest version. Free graphical applications that embed pngcrush are also noted by the maker.

XConvert Image Compressor is a web-based tool for compressing, resizing, and converting images, with batch processing and API access. It supports formats including JPG, JPEG, JFIF, PNG, WebP, HEIC, AVIF, GIF, BMP, TIFF, ICO, PPM, EPS, and several RAW formats. Images can be uploaded from a computer, Google Drive, or Dropbox. Compression can be combined with conversion to JPG, WebP, AVIF, PNG, or HEIC; metadata controls and Auto Scale are also available. Auto Scale adjusts dimensions to meet a target file size while maximizing quality. Free users can compress images up to 300 MB each, with no per-session file-count cap. Free video conversions are also offered: visitors get 30 daily, and free accounts get 60. Basic costs $4.99 a month or 49.99 USD yearly; Pro costs $9.99 a month or 99.99 USD yearly. The service says uploads use TLS in transit and files are automatically deleted after a few hours. No account is required for the online tool, and an XConvert desktop app supports offline conversion and editing.