FileOptimizer vs Zstandard

FileOptimizer is a free Windows program that recompresses already-compressed files to reduce their size while retaining their format and behavior. It supports batch processing and accepts files through its interface or command line; optimization replaces them with optimized versions. The maker says it handles more than 600 file extensions and identifies types by examining file contents, regardless of extension. Listed formats include APNG, AVIF, BMP, BPG, DDS, DNG, GIF, HEIC, HEIF, ICO, J2C, J2K, JP2, JPEG, JPG, JXL, MNG, MPO, PCX, PNG, PSD, SVG, TGA, TIF, TIFF, and WEBP. By default, it removes extra metadata and keeps originals in the recycle bin. The program includes more than 90 third-party tools as plugins and supports command-line automation. It is provided under the GNU Affero General Public License, free for personal and commercial use without feature limits. The maker lists Windows XP through Windows 11 and Server 2022 among its requirements. Lossy options are also documented for PNG, JPEG, and GIF.

Zstandard is a lossless compression algorithm for real-time workloads, with controls that let users shift compression speed and ratio in small increments. Its reference implementation includes a C library and a command-line utility that creates and decodes .zst, .gz, .xz, and .lz4 files. The format is stable and documented in RFC 8878; the implementation is available under BSD or GPLv2. For small, related samples, training can produce a data-specific dictionary to improve compression. The same dictionary must be present for both compression and decompression, and the samples need to be correlated; there is no universal dictionary. The project documents builds with Make, CMake, Meson, Visual Studio, Buck, and Bazel, plus installation using vcpkg and Conan. Community bindings and ports are listed for languages including Python, Rust, Java, C#, JavaScript, Go, PHP, and Swift. Zstandard is free, with a free plan, and supports Linux, Windows, and macOS.