What is syv?

syv is a single-file Python command-line tool that speeds up websites by handling two specific tasks: compressing frontend build files and saving static copies of dynamic web pages. It sits between your development code and your production web server, preparing files so the server can deliver them faster. For frontend builds, syv scans your compiled JavaScript and CSS files, creates compressed versions of each file (using gzip), and adds version hashes to asset URLs in your HTML files. Adding a hash to a URL (such as turning "app.js" into "app.js?v=e3b0c4") forces browsers to fetch fresh copies of files whenever the content changes, while still allowing long-term caching when nothing has changed. This process runs across multiple CPU threads in parallel, so it completes quickly even with large numbers of files. For static site generation, syv acts as a simple web crawler. It reads your site's sitemap, visits each URL on your local server, saves the resulting HTML to a cache folder, and records how long each cached page should stay valid. When a visitor requests one of those pages, your web server can serve the saved HTML directly instead of running backend code each time. The tool has a live watch mode for development: it monitors your files for changes and re-runs the build process automatically. There is also a dry-run mode to preview what syv would do without writing anything to disk. Syv is written entirely using Python's standard library, so it requires no installation of packages and no virtual environment. You download a single file, make it executable, and place it in your system path. It runs on Linux, macOS, Windows, and Termux (the Android terminal environment). The v5.1 release added security checks to block server-side request forgery, path traversal attacks, and symlink following, and added automatic fallback to sequential processing if memory runs low during large builds.