Extremely fast non-cryptographic hash algorithm

https://xxhash.com/ https://github.com/Cyan4973/xxHash

XKB keyboard layout indicator and switcher

https://sourceforge.net/projects/xxkb/

Puzzle games like sokoban or boulderdash

https://xye.sourceforge.net/

Infocom game interpreter that runs under X11

https://www.eblong.com/zarf/xzip.html

Magnify, rotate, mirror the image on the X screen

Yet another Basic for Unix and Windows

http://www.yabasic.de/

Original free open-source forum written in Perl

http://www.yabbforum.com/

Display GNOME dialogs from the command line

https://github.com/v1cont/yad

Yet another FTP client, similar to ftp(1)

https://github.com/sebastinas/yafc

Yet Another File Integrity Checker, similar to Tripwire

http://philosophysw.com/software/yafic/

Curses version of the dice game for one or more players

Portable JSON parsing and serialization library in ANSI C

http://lloyd.github.com/yajl/

Enhanced execution box with regex pattern matching

http://offog.org/code/

YAML parser and emitter in C++ matching the YAML 1.2 spec

https://github.com/jbeder/yaml-cpp

Simple command line tool for formatting yaml files

https://github.com/google/yamlfmt

Package manager for node, alternative to npm (meta port)

https://classic.yarnpkg.com/

Package manager for node, alternative to npm

https://classic.yarnpkg.com/

Package manager for node, alternative to npm

https://classic.yarnpkg.com/

Package manager for node, alternative to npm

https://classic.yarnpkg.com/

Default GTK theme for Ubuntu

https://github.com/ubuntu/yaru

POSIX-compliant command line shell

https://magicant.github.io/yash/

Complete rewrite of the NASM assembler

https://yasm.tortall.net/

General-purpose console screen reader

https://yasr.sourceforge.net/

Yet Another LaTeX mode and html mode on Emacs

http://www.yatex.org/

Z39.50/SR client and API library

https://www.indexdata.com/resources/software/yaz/

Yet another Canna client for Emacs

http://www.ceres.dti.ne.jp/~knak/yc.html

Diff readability enhancher for color terminals

https://github.com/ymattw/ydiff

Terminal wrapper for creating drop-down consoles

http://phrat.de/yeahtools.html

Minimal X11 window manager with BeOS-like tabbed titles

http://phrat.de/

Help browser for the GNOME desktop

https://www.gnome.org/

Utilities to help manage documentation for Yelp and the web

https://wiki.gnome.org/Apps/Yelp/Tools

DocBook XSLT stylesheets for yelp

https://www.gnome.org/

Free (GPL) encoder and decoder for the yEnc Usenet file format

http://www.yencode.org/

Amateur Radio curses based logging program

https://fkurz.net/ham/yfklog.html

SMT solver

https://yices.csl.sri.com/ https://github.com/SRI-CSL/yices2/

Convert between YAML, TOML, JSON, and HCL

https://github.com/sclevine/yj

Command line tool that converts YAML to JSON

https://github.com/bruceadams/yj

Yubico C client library

https://developers.yubico.com/yubico-c-client/

Library and tool for personalization of Yubico's YubiKey

https://developers.yubico.com/yubikey-personalization/

Youtube videos downloader

https://github.com/kkdai/youtube

Command-line YAML and XML processor, jq wrapper for YAML/XML documents

https://kislyuk.github.io/yq/

Improved version of Icculus Quake II

https://www.yamagi.org/quake2/

Command-line program for downloading videos from various platforms

https://github.com/yt-dlp/yt-dlp

Unpack data in MS Outlook TNEF format

https://github.com/Yeraze/ytnef

Yubico PIV tool

https://developers.yubico.com/yubico-piv-tool/

Multi-lingual Unicode text editor with TTF support

https://www.yudit.org/

The Yahoo! JavaScript and CSS Compressor

https://yui.github.io/yuicompressor/

Encrypted peer-to-peer IPv6 UDP messaging terminal

https://github.com/yamafaktory/yume

Tool to decode yEnc encoded files

http://yydecode.sf.net/

Fastest JSON library in C

https://github.com/ibireme/yyjson