ytdl-org/youtube-dl

youtube-dl is a command-line program for downloading videos from YouTube and a number of other video sites. The README states the basic facts plainly: it needs a Python interpreter, version 2.6, 2.7, or 3.2 or newer, is not platform specific, and runs on Unix, Windows, and macOS. It is released into the public domain, which the README explains means anyone can modify, redistribute, or use it however they like. Usage is the program name followed by one or more URLs and any options. The Installation section gives several routes. On Unix systems, the suggested approach is a curl or wget command that downloads the binary to /usr/local/bin and marks it executable. Windows users can download an .exe file and put it anywhere on their PATH, with a warning not to drop it inside the System32 folder. The README also covers pip install for upgrading, brew install for macOS through Homebrew, and port install through MacPorts. A pointer to a download page mentions PGP signatures for users who want to verify a release. The OPTIONS section is the largest part of the document and is a printed copy of the program help text. Top-level flags include help, version, self-update, ignore-errors, abort-on-error, list-extractors, force-generic-extractor, default-search prefixes, config file loading rules, flat-playlist listing, mark-watched, and a no-color switch. The text is grouped into subsections: Network Options for proxies, socket timeouts, source address, and forced IPv4 or IPv6, Geo Restriction options that can fake X-Forwarded-For headers or pin a country code, and Video Selection options that let users pick playlist ranges and specific items. Later sections of the README describe the configuration file, the output template that controls filenames, format selection rules for choosing video and audio streams, FAQ entries, developer instructions for working with the git checkout, an Embedding section for using youtube-dl from inside other Python programs, a Bugs section that explains how to file good reports, and a Copyright section. Someone would use this program when they want a scriptable way to fetch a video file from a public web video site for offline viewing.