Installation

The stable version of this package is maintained on pypi, install or upgrade, using pip:

pip install --upgrade wcwidth

Problem

All Python string-formatting functions, textwrap.wrap(), str.ljust(), str.rjust(), and str.center() incorrectly measure the displayed width of a string as equal to the number of their codepoints.

Some examples of incorrect results:

>>> # result consumes 16 total cells, 11 expected,
>>> 'コンニチハ'.rjust(11, 'X')
'XXXXXXコンニチハ'

>>> # result consumes 5 total cells, 6 expected,
>>> 'café'.center(6, 'X')
'caféX'

Solution

The lowest-level functions in this library are derived from POSIX.1-2001 and POSIX.1-2008 wcwidth(3) and wcswidth(3), which this library precisely copies by interface as wcwidth() and wcswidth(). These functions return -1 when C0 and C1 control codes are present.

An easy-to-use width() function is provided as a wrapper of wcswidth() that is also capable of measuring most terminal control codes and sequences, like colors, bold, tabstops, and horizontal cursor movement. width() argument term_program may provide more accurate terminal measurement Corrections as a wrapper of wcstwidth().

Text-justification is solved by the sequence-aware functions ljust(), rjust(), center(), and the grapheme-aware function wrap(), serving as drop-in replacements to python standard functions.

The clip() function extracts substrings by their displayed column positions, and strip_sequences() removes terminal escape sequences from text altogether.

The iterator functions iter_graphemes() and iter_sequences() allow for careful navigation of grapheme and terminal control sequence boundaries as required by editors or REPLs with cursor control. iter_graphemes_reverse() and grapheme_boundary_before() are necessary for backward cursor control over complex unicode.

Discrepancies

You may find that support varies for complex unicode sequences or codepoints.

This library may be considered to presume the terminal is enabled for DEC Private Mode 2027 (“Grapheme Clustering”) by default, which may require to be enabled by a TUI application but is often the default mode for those terminals that support it.

This library does support any specific “legacy width” measurement by API, but it does provide Corrections for those terminals without grapheme support.

See also:

• terminal-unicode-core.tex (2021)

• Grapheme Clusters and Terminal Emulators (2023)

• State of Terminal Emulators in 2025

• Perfecting Terminal Character Width Using Correction Tables (2026)

The jquast/ucs-detect project publishes automatic results of compliance to our standard for Wide character, Languages, grapheme clustering, complex or combining scripts, emojis, zero-width joiner, variations, and regional indicator (flags) as a General Tabulated Summary by terminal emulator software and version. The results of the ucs-detect project create our correction tables.

wcwidth()

Measures width of a single codepoint,

>>> # '♀' narrow emoji
>>> wcwidth.wcwidth('\u2640')
1

Use function wcwidth() to determine the length of a single unicode character.

See specification of character measurements. Note that -1 is returned for control codes.

wcswidth()

Measures width of a string, returns -1 for control codes.

>>> # '♀️' emoji w/vs-16
>>> wcwidth.wcswidth('\u2640\ufe0f')
2

Use function wcswidth() to determine the length of many, a string of unicode characters.

See specification of character measurements. Note that -1 is returned if control codes occurs anywhere in the string.

wcstwidth()

Same behavior as wcswidth() with automatic terminal-specific Corrections, reading TERM_PROGRAM or TERM when True (default), or caller can provide terminal query XTVERSION or ENQ response:

>>> # '♀️' emoji w/vs-16, uncorrected:
>>> wcwidth.wcswidth('\u2640\ufe0f')
2
>>> # corrected,
>>> wcwidth.wcstwidth('\u2640\ufe0f', term_program='vte')
1

width()

Use function width() to measure a string with improved handling of control_codes and measurement Corrections through term_program:

>>> # same support as wcswidth(), eg. regional indicator flag:
>>> wcwidth.width('\U0001F1FF\U0001F1FC')
2
>>> # set term_program=True to use wcstwidth()
>>> wcwidth.width('\U0001F1FF\U0001F1FC', term_program=True)
1
>>> # or set term_program for measurement of a specific terminal
>>> wcwidth.width('\U0001F1FF\U0001F1FC', term_program='contour')
2
>>> # but also supports sequences, like SGR colored text, "WARN", followed by reset
>>> wcwidth.width('\x1b[38;2;255;150;100mWARN\x1b[0m')
4
>>> # tabs are measured as though the string begins at a tabstop,
>>> wcwidth.width('\t', tabsize=4)
4
>>> # or, all control characters can be ignored (including tab)
>>> wcwidth.width('\t\n\a\r', control_codes='ignore')
0
>>> # sequences with "indeterminate" effects like Home + Clear are zero-width
>>> wcwidth.width('\x1b[H\x1b[2J')
0
>>> # horizontal cursor movements are parsed,
>>> wcwidth.width('hello\b\b\b\b\bworld')
5
>>> wcwidth.width('hello\x1b[5Dworld')
5
>>> # or ignored,
>>> wcwidth.width('hello\x1b[5Dworld', control_codes='ignore')
10
>>> # Measure width of text using kitty text sizing protocol (OSC 66),
>>> width('\x1b]66;w=2;XY\x07')
2
>>> # Scaled text sizing: each grapheme occupies 'scale' cells
>>> width('\x1b]66;s=2;ABC\x07')
6

Use control_codes='ignore' when the input is known not to contain any control characters or terminal sequences for slightly improved performance. Note that TAB ('\t') is a control character and is also ignored, you may want to use str.expandtabs(), first.

Use control_codes='strict' when input is known to contain some control sequences, such as SGR color, bold, hyperlinks and cursor movement. Any sequence that cannot be accurately parsed for horizontal measurement, such as clearing the screen, vertical, or absolute cursor movement will raise ValueError:

>>> # or, raise ValueError for "indeterminate" effects using control_codes='strict'
>>> wcwidth.width('\n', control_codes='strict')
Traceback (most recent call last):
...
ValueError: Vertical movement character 0xa at position 0


>>> wcwidth.width('\x1b[H\x1b[2J', control_codes='strict')
Traceback (most recent call last):
...
ValueError: Indeterminate cursor sequence at position 0, '\x1b[H'


>>> # cursor left movement beyond string start raises in strict mode,
>>> wcwidth.width('a\x1b[5Da', control_codes='strict')
Traceback (most recent call last):
...
ValueError: Cursor left movement at position 1 would move 5 cells left from column 1, exceeding string start

iter_sequences()

Iterates through text, segmented by terminal sequence,

>>> list(wcwidth.iter_sequences('hello'))
[('hello', False)]
>>> list(wcwidth.iter_sequences('\x1b[31mred\x1b[0m'))
[('\x1b[31m', True), ('red', False), ('\x1b[0m', True)]

Use iter_sequences() to split text into segments of plain text and escape sequences. Each tuple contains the segment string and a boolean indicating whether it is an escape sequence (True) or text (False).

iter_graphemes()

Use iter_graphemes() to iterate over grapheme clusters of a string.

>>> from wcwidth import iter_graphemes
>>> # ok + Regional Indicator 'Z', 'W' (Zimbabwe)
>>> list(wcwidth.iter_graphemes('ok\U0001F1FF\U0001F1FC'))
['o', 'k', '🇿🇼']

>>> # cafe + combining acute accent
>>> list(wcwidth.iter_graphemes('cafe\u0301'))
['c', 'a', 'f', 'é']

>>> # ok + Emoji Man + ZWJ + Woman + ZWJ + Girl
>>> list(wcwidth.iter_graphemes('ok\U0001F468\u200D\U0001F469\u200D\U0001F467'))
['o', 'k', '👨\u200d👩\u200d👧']

A grapheme cluster is what a user perceives as a single character, even if it is composed of multiple Unicode codepoints. This function implements Unicode Standard Annex #29 grapheme cluster boundary rules.

ljust()

Use ljust() as replacement of str.ljust():

>>> 'コンニチハ'.ljust(11, '*')             # don't do this
'コンニチハ******'
>>> wcwidth.ljust('コンニチハ', 11, '*')    # do this!
'コンニチハ*'

rjust()

Use rjust() as replacement of str.rjust():

>>> 'コンニチハ'.rjust(11, '*')             # don't do this
'******コンニチハ'
>>> wcwidth.rjust('コンニチハ', 11, '*')    # do this!
'*コンニチハ'

center()

Use center() as replacement of str.center():

>>> 'cafe\u0301'.center(6, '*')             # don't do this
'café*'
>>> wcwidth.center('cafe\u0301', 6, '*')
'*café*'                                    # do this!

wrap()

Use function wrap() to wrap text containing terminal sequences, Unicode grapheme clusters, and wide characters to a given display width.

>>> from wcwidth import wrap
>>> # Basic wrapping
>>> wrap('hello world', 5)
['hello', 'world']

>>> # Wrapping CJK text (each character is 2 cells wide)
>>> wrap('コンニチハ', 4)
['コン', 'ニチ', 'ハ']

>>> # Text with ANSI color sequences - SGR codes are propagated by default
>>> # Each line ends with reset, next line starts with restored style
>>> wrap('\x1b[1;31mhello world\x1b[0m', 5)
['\x1b[1;31mhello\x1b[0m', '\x1b[1;31mworld\x1b[0m']

clip()

Use clip() to extract a substring by column positions, preserving terminal sequences.

>>> from wcwidth import clip
>>> # Wide characters split to Narrow boundaries using fillchar=' '
>>> clip('中文字', 0, 3)
'中 '
>>> clip('中文字', 1, 5, fillchar='.')
'.文.'

>>> # 'end' defaults to -1, meaning "to the end of the line"
>>> clip('中文字', 1)
' 文字'
>>> clip('\x1b[1;31mHello world\x1b[0m', 6)
'\x1b[1;31mworld\x1b[0m'

>>> # SGR codes are propagated by default - result begins with active style
>>> # and ends with reset if styles are active
>>> clip('\x1b[1;31mHello world\x1b[0m', 6, 11)
'\x1b[1;31mworld\x1b[0m'

>>> # Disable SGR propagation to preserve sequence order outside of clip boundary
>>> clip('\x1b[31m中文\x1b[32m', 0, 3, propagate_sgr=False)
'\x1b[31m中 \x1b[32m'

>>> # Cursor-left overwrites previous text (painter's algorithm)
>>> clip('hello\x1b[2DXY', 0, 5)
'helXY'
>>> # Carriage return resets to column 0, overwriting earlier cells
>>> clip('abc\rXY', 0, 5)
'XYc'

>>> # even OSC 8 hyperlink text may be clipped, 'Click This link' -> 'is link' !
>>> clip('\x1b]8;;http://example.com\x07Click This link\x1b]8;;\x07', 8, 15)
'\x1b]8;;http://example.com\x07is link\x1b]8;;\x07'

>>> # and OSC 66 kitty text sizing, supporting width and scale, 'Look' -> '...ook'
>>> clip('\x1b]66;w=4:s=4;Look\x07', 1, 16, fillchar='.')
'...\x1b]66;s=4:w=3;ook\x07'

Use overtyping=False when the input is known not to contain any cursor movement characters (\b, \r, CSI C, CSI D, CSI G) for improved performance. When overtyping=None (default), a slower “Painter’s algorithm” may be used after testing for the presence of these characters. overtyping has no effect when control_codes='ignore'.

strip_sequences()

Use strip_sequences() to remove all terminal escape sequences from text.

>>> from wcwidth import strip_sequences
>>> strip_sequences('\x1b[31mred\x1b[0m')
'red'

Ambiguous Width

Some Unicode characters have “East Asian Ambiguous” (A) width. These characters display as 1 cell by default, matching Western terminal contexts, but many CJK (Chinese, Japanese, Korean) environments may have a preference for 2 cells. This is often found as boolean option, “Ambiguous width as wide” in Terminal Emulator software preferences.

The ambiguous_width parameter is available on all width-measuring functions: wcwidth(), wcswidth(), width(), ljust(), rjust(), center(), wrap(), and clip().

By default, wcwidth treats ambiguous characters as narrow (width 1). For CJK environments where your terminal is configured to display ambiguous characters as double-width, pass ambiguous_width=2:

>>> # CIRCLED DIGIT ONE - ambiguous width
>>> wcwidth.width('\u2460')
1
>>> wcwidth.width('\u2460', ambiguous_width=2)
2

Terminal Detection

The most reliable method to detect whether a terminal profile is set for “Ambiguous width as wide” mode is to display an ambiguous character surrounded by a pair of Cursor Position Report (CPR) queries with a terminal in cooked or raw mode, and to parse the responses for their (y, x) locations and measure the difference x.

This code should also be careful to check whether it is attached to a terminal and be careful of possible timeout, slow network, or non-response when working with “dumb terminals” like a CI build.

jquast/blessed library provides such a helping Terminal.detect_ambiguous_width() method:

>>> import blessed, functools
>>> # Detect terminal ambiguous width as wide (2) or narrow (1)
>>> ambiguous_width = blessed.Terminal().detect_ambiguous_width()
>>> # Define a new 'width' function with this argument
>>> awidth = functools.partial(wcwidth.width, ambiguous_width=ambiguous_width)
>>> # result depends on attached terminal mode
>>> awidth('\u2460')
1

Corrections

Corrections may be automatically applied depending on the detected or given terminal software name beginning with wcwidth release 0.8.0. This allows to correct widths for terminal software that differs from the python wcwidth specification. These corrections are sourced from the jquast/ucs-detect project.

The term_program parameter is available on all width-measuring functions: wcstwidth(), width(), ljust(), rjust(), center(), wrap(), and clip().

wcstwidth() defaults to term_program=True, auto-detecting the terminal from the TERM_PROGRAM or TERM environment variable. All other functions default to term_program=False, disabling corrections. Use term_program=True for automatic detection by environment values of TERM and TERM_PROGRAM.

# VTE terminals (Gnome Terminal Et al.) still render trigrams as narrow (1 cell), but their
# definition was changed to wide in Unicode 16 (September 2024).
>>> wcwidth.wcswidth('\u2630')
2
>>> wcwidth.wcstwidth('\u2630', term_program='vte')
1

# account for Alacritty non-support of emoji ZWJ:
# man + ZWJ + woman + ZWJ + girl + ZWJ + boy
>>> family = '\U0001F468\u200D\U0001F469\u200D\U0001F467\u200D\U0001F466'
>>> wcwidth.wcswidth(family)
2
>>> wcwidth.wcstwidth(family, term_program='alacritty')
8

Only detectable terminals are included: those that identify themselves by XTVERSION, ENQ, any TERM_PROGRAM or a unique TERM environment value. For the most accurate correction tables, query the terminal’s software version via XTVERSION (CSI > q) using a higher-level interactive terminal library like jquast/blessed:

>>> import blessed, wcwidth
>>> term = blessed.Terminal()
>>> sw_ver = term.get_software_version()
>>> print(sw_ver)
SoftwareVersion(name='VTE', version='7600')
>>> wcwidth.width('\u2630', term_program=sw_ver.name)
1

This is important because TERM_PROGRAM is not forwarded for remote hosts, like SSH, and many terminals may only be identified using XTVERSION or ENQ. Use list_term_programs() to see all recognized names:

>>> wcwidth.list_term_programs()
('absolutetelnet/ssh', 'alacritty', 'apple_terminal', 'bobcat', 'contour',
 'extraterm', 'foot', 'ghostty', 'hyper', 'iterm.app', 'iterm2', 'kitty',
 'konsole', 'mintty', 'mlterm', 'pterm', 'putty', 'rio', 'rxvt',
 'rxvt-unicode-256color', 'st', 'st-256color', 'tabby', 'terminology',
 'urxvt', 'vscode', 'vte', 'warp', 'warpterminal', 'wezterm', 'xterm',
 'xterm-ghostty', 'xterm-kitty', 'xterm.js')

term_program=False (the default for width(), ljust(), rjust(), center(), wrap(), and clip()) disables terminal corrections.

For automatic tests and other purposes that require cross-environment consistency, set static values or unset TERM and TERM_PROGRAM environment values, such as in conftest.py with pytest:

@pytest.fixture(autouse=True)
def _clear_term_program():
    """unset TERM/TERM_PROGRAM before each test."""
    saved_term = os.environ.pop('TERM', None)
    saved_tprog = os.environ.pop('TERM_PROGRAM', None)
    yield
    if saved_term is not None:
        os.environ['TERM'] = saved_term
    if saved_tprog is not None:
        os.environ['TERM_PROGRAM'] = saved_tprog