A fast side-by-side diff tool with syntax highlighting and images

Major Features#

  • Displays diffs side-by-side in the kitty terminal

  • Does syntax highlighting of the displayed diffs, asynchronously, for maximum speed

  • Displays images as well as text diffs, even over SSH

  • Does recursive directory diffing

Screenshot, showing a sample diff

Screenshot, showing a sample diff#


Simply install kitty.


In the kitty terminal, run:

kitten diff file1 file2

to see the diff between file1 and file2.

Create an alias in your shell’s startup file to shorten the command, for example:

alias d="kitten diff"

Now all you need to do to diff two files is:

d file1 file2

You can also pass directories instead of files to see the recursive diff of the directory contents.

Keyboard controls#




Q, Esc

Scroll line up

K, Up

Scroll line down

J, Down

Scroll page up


Scroll page down


Scroll to top


Scroll to bottom


Scroll to next page

Space, PgDn

Scroll to previous page


Scroll to next change


Scroll to previous change


Increase lines of context


Decrease lines of context


All lines of context


Restore default context


Search forwards


Search backwards


Clear search


Scroll to next match

>, .

Scroll to previous match

<, ,

Copy selection to clipboard


Copy selection or exit


Integrating with git#

Add the following to ~/.gitconfig:

    tool = kitty
    guitool = kitty.gui
    prompt = false
    trustExitCode = true
[difftool "kitty"]
    cmd = kitten diff $LOCAL $REMOTE
[difftool "kitty.gui"]
    cmd = kitten diff $LOCAL $REMOTE

Now to use kitty-diff to view git diffs, you can simply do:

git difftool --no-symlinks --dir-diff

Once again, creating an alias for this command is useful.

Why does this work only in kitty?#

The diff kitten makes use of various features that are kitty only, such as the kitty graphics protocol, the extended keyboard protocol, etc. It also leverages terminal program infrastructure I created for all of kitty’s other kittens to reduce the amount of code needed (the entire implementation is under 3000 lines of code).

And fundamentally, it’s kitty only because I wrote it for myself, and I am highly unlikely to use any other terminals :)


You can configure the colors used, keyboard shortcuts, the diff implementation, the default lines of context, etc. by creating a diff.conf file in your kitty config folder. See below for the supported configuration directives.


syntax_aliases pyj:py pyi:py recipe:py

File extension aliases for syntax highlight. For example, to syntax highlight as use a setting of xyz:abc. Multiple aliases must be separated by spaces.

num_context_lines 3

The number of lines of context to show around each change.

diff_cmd auto

The diff command to use. Must contain the placeholder _CONTEXT_ which will be replaced by the number of lines of context. A few special values are allowed: auto will automatically pick an available diff implementation. builtin will use the anchored diff algorithm from the Go standard library. git will use the git command to do the diffing. diff will use the diff command to do the diffing.

replace_tab_by \x20\x20\x20\x20

The string to replace tabs with. Default is to use four spaces.


A glob pattern that is matched against only the filename of files and directories. Matching files and directories are ignored when scanning the filesystem to look for files to diff. Can be specified multiple times to use multiple patterns. For example:

ignore_name .git
ignore_name *~
ignore_name *.pyc


pygments_style default

The pygments color scheme to use for syntax highlighting. See pygments builtin styles for a list of schemes. Note that this does not change the colors used for diffing, only the colors used for syntax highlighting. To change the general colors use the settings below.

foreground, background#
foreground black
background white

Basic colors

title_fg, title_bg#
title_fg black
title_bg white

Title colors

margin_bg, margin_fg#
margin_bg #fafbfc
margin_fg #aaaaaa

Margin colors

removed_bg, highlight_removed_bg, removed_margin_bg#
removed_bg           #ffeef0
highlight_removed_bg #fdb8c0
removed_margin_bg    #ffdce0

Removed text backgrounds

added_bg, highlight_added_bg, added_margin_bg#
added_bg           #e6ffed
highlight_added_bg #acf2bd
added_margin_bg    #cdffd8

Added text backgrounds

filler_bg #fafbfc

Filler (empty) line background

margin_filler_bg none

Filler (empty) line background in margins, defaults to the filler background

hunk_margin_bg, hunk_bg#
hunk_margin_bg #dbedff
hunk_bg        #f1f8ff

Hunk header colors

search_bg, search_fg, select_bg, select_fg#
search_bg #444
search_fg white
select_bg #b4d5fe
select_fg black


Keyboard shortcuts#

map q quit
map esc quit
Scroll down#
map j scroll_by 1
map down scroll_by 1
Scroll up#
map k scroll_by -1
map up scroll_by -1
Scroll to top#
map home scroll_to start
Scroll to bottom#
map end scroll_to end
Scroll to next page#
map page_down scroll_to next-page
map space scroll_to next-page
Scroll to previous page#
map page_up scroll_to prev-page
Scroll to next change#
map n scroll_to next-change
Scroll to previous change#
map p scroll_to prev-change
Show all context#
map a change_context all
Show default context#
map = change_context default
Increase context#
map + change_context 5
Decrease context#
map - change_context -5
Search forward#
map / start_search regex forward
Search backward#
map ? start_search regex backward
Scroll to next search match#
map . scroll_to next-match
map > scroll_to next-match
Scroll to previous search match#
map , scroll_to prev-match
map < scroll_to prev-match
Search forward (no regex)#
map f start_search substring forward
Search backward (no regex)#
map b start_search substring backward
Copy selection to clipboard#
map y copy_to_clipboard
Copy selection to clipboard or exit if no selection is present#
map ctrl+c copy_to_clipboard_or_exit

Source code for diff#

The source code for this kitten is available on GitHub.

Command Line Interface#

kitty +kitten diff [options] file_or_directory_left file_or_directory_right

Show a side-by-side diff of the specified files/directories. You can also use ssh:hostname:remote-file-path to diff remote files.


--context <CONTEXT>#

Number of lines of context to show between changes. Negative values use the number set in diff.conf. Default: -1

--config <CONFIG>#

Specify a path to the configuration file(s) to use. All configuration files are merged onto the builtin diff.conf, overriding the builtin values. This option can be specified multiple times to read multiple configuration files in sequence, which are merged. Use the special value NONE to not load any config file.

If this option is not specified, config files are searched for in the order: $XDG_CONFIG_HOME/kitty/diff.conf, ~/.config/kitty/diff.conf, $XDG_CONFIG_DIRS/kitty/diff.conf. The first one that exists is used as the config file.

If the environment variable KITTY_CONFIG_DIRECTORY is specified, that directory is always used and the above searching does not happen.

If /etc/xdg/kitty/diff.conf exists, it is merged before (i.e. with lower priority) than any user config files. It can be used to specify system-wide defaults for all users. You can use either - or /dev/stdin to read the config from STDIN.

--override <OVERRIDE>, -o <OVERRIDE>#

Override individual configuration options, can be specified multiple times. Syntax: name=value. For example: -o background=gray

Sample diff.conf#

You can download a sample diff.conf file with all default settings and comments describing each setting by clicking: sample diff.conf.