rxvt-unicode

rxvt-unicode, usually run as urxvt, is a fork of the rxvt terminal emulator for X11, written in C++ by Marc Lehmann. It stores text in Unicode, follows the system locale for input, output and character widths, and can mix several fonts at once, combining Xft and core X fonts. It suits people on Linux or BSD X11 desktops who want a small, long-established terminal that they configure through X resources and extend with Perl.

Settings are X resources under the URxvt (or Rxvt) class, read from ~/.Xdefaults, the root window's RESOURCE_MANAGER property (typically loaded from ~/.Xresources with xrdb -merge), $XENVIRONMENT and -xrm on the command line, and every resource is also available as a long command-line option. Everything is documented in man pages: urxvt(1), urxvt(7) (the FAQ) and urxvtperl(3). Daemon mode runs urxvtd as one process that opens windows on request from urxvtc, which saves memory and startup time, and the FAQ includes systemd socket and service units for it.

Much of the interactive behaviour comes from the embedded Perl interpreter and the extensions shipped with it, enabled through the perl-ext-common resource and searched in ~/.urxvt/ext among other paths. The bundled tabbed extension adds a simple tab bar (urxvt -pe tabbed), matcher underlines and opens URLs, and others provide regex-based selection, selection popup menus, scrollback search and paste confirmation. Lines are re-wrapped on resize, combining characters are supported, and background images and tinting are available when built with an image library.

rxvt-unicode renders through X11 on the CPU, has no native Wayland support, and does not implement programming-font ligatures or an inline image protocol such as Sixel. The project page lists complex scripts such as Arabic and right-to-left rendering as missing and points to mlterm for those. Development happens in CVS rather than on a code-hosting platform, and the last release, 9.31 from January 2023, fixed CVE-2022-4170; later fixes are in CVS but have not been released.