When comparing KiTTY vs rxvt-unicode, the Slant community recommends rxvt-unicode for most people. In the question“What are the best terminal emulators for UNIX-like systems?” rxvt-unicode is ranked 1st while KiTTY is ranked 2nd. The most important reason people chose rxvt-unicode is:
Rxvt-unicode uses very little memory and takes a lightweight approach without losing many important functionalities. A single instance of urxvt takes about 6.5MB-8MB of RAM.
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Pros
Pro Includes additional features over PuTTy
- Sessions filter
- Shortcuts for pre-defined command
- The session launcher
- Automatic logon script
- URL hyperlinks
- Running a locally saved script on a remote session
- Send to tray
- Transparency
- Quick start of a duplicate session
- SSH Handler: Internet Explorer integration
- pscp.exe and WinSCP integration
- New command-line options
Pro Startup sessions
Support start-up sessions which allow you to specify the window/tab layout, working directories, and programs to run on startup.
Pro Source Code Available
Source code is available so you could modify or review changes.
Pro Can store login credentials
Ability to store passwords/passphrases locally.
Pro Clickable URLs
URLs are parsed and can be clicked.
Pro Auto login script
Automatic processing of commands after conncetion was made.
Pro True Color support
Supports True Color, so software like Vim can display a really nice pallet.
Pro Portable version available
Pro Background image
Ability to overlay the terminal background with an image.
Pro Unicode
Uses Unicode for the best character compatibility.
Pro Low memory usage
Rxvt-unicode uses very little memory and takes a lightweight approach without losing many important functionalities. A single instance of urxvt takes about 6.5MB-8MB of RAM.
Pro Can be daemonized to reduce resource usage
For those who want to lower their system's resource usage, rxvt-unicode allows for daemonization. This way you can run several instances of urxvt inside a single process.
Pro Supports terminal transparency
Changing the transparency of the terminal is allowed for in rxvt-unicode. This not only makes for eye candy but is also good for GUI usability.
Pro Minimum dependencies and simple text config
Pro Supports multiple font types
Multiple font types can be displayed flawlessly in rxvt-unicode.
Pro Handles bold text colour properly
Displays characters with text attribute bold actually as bold glyphs.
Pro High performance
Rxvt-unicode is much faster than most alternatives.
Pro Unicode support
International language support is provided through Unicode.
Pro Proper wrapping support
During selection and pasting wrapped text doesn't break into lines at place of wrapping.
Pro Fast text rendering
Rxvt-unicode has very fast text rendering, being able to render hundreds of MB of text in a very short time.
Pro Built-in Perl interpreter
It has a built-in Perl interpreter, meaning that no install is needed. Simply run urxvtperl
.
Cons
Con No centralized configuration
Each session holds its own configuration of all features. This means that if one wants to change a configuration common to all sessions (say, the terminal font), it has to be changed in each stored session separately.
A better solution would be to have a default configuration and store only the changed elements for each session (both configurations would be merged, with e priority on the specific one).
Con No tabbed sessions
No built-in support for tabbed sessions. Requires an add-on.
Con No mouse support in alternative screens
Like vim, less, etc.
Con Unicode characters that are too wide are blanked instead of clipped
If a character in a backup font is wider than the base font, urxvt substitutes the non-displayable character. A large letter space will show the wide characters, but the result is not reasonably spaced. There is a patch from 2014 that the urxvt maintainer will not merge.
Con Requires work to look acceptable
Out of the box, rxvt-unicode is not too pleasant to look at. Some understanding of Xresources is required for updating its appearance. That being said, the experience of customizing it can be very rewarding.
Con Requires work to configure useful functionality (clickable URL's, font scaling, tabs)
Con In daemon mode you can lose all your terminals
Because of sharing the same process terminal windows cannot be killed without sacrificing all other open windows. That becomes even more dangerous if you use multiple graphical managers without overriding socket with RXVT_SOCKET.
Con Unicode rendering is buggy
There are a few references to urxvt's buggy rendering, such as unicode combining characters, which bled through during scrolling.
Con Bloated
Exists because Xterm is complete trash. Although it has a lot of features, you will most likely never use them all.
Con No support yet for 24-bit "True Color"
Though this is still not available, you can download the patched version for 24bit, here.
Con Font size cannot be changed on the fly with the mousewheel
Sometimes you may need to enlarge the font to improve readability, or shrink it to have more real estate and "hawk's eye" view of data. In rxvt you need to change the configuration file or use these commands:
$ function fontsize
{printf '\33]50;%s%d\007' "xft:Dejavu Sans Mono:size=$1::antialias=false"}
$ fontsize 22
Con No option to have a "reverse color" cursor
While you can choose the color of the cursor and the character under the cursor, there's no automatic "reverse color" for the cursor. This makes it impossible to use rxvt-unicode if you have a light background terminal and a dark background editor.