utf8x vs. utf8 (inputenc)

Question

I normally use \usepackage[utf8]{inputenc} for my latex document but on this site i saw a lot of code with \usepackage[utf8x]{inputenc}.

What are the differences between the 2 options ?

Is there one of the option obsolete and which one should I use ?

Answer 1

The simple answer is that utf8x is to be avoided if possible. It loads the ucs package, which for a long time was unmaintained (although there is now a new maintainer) and breaks various other things.

See egreg's answer to this question as well, which outlines how to get extra characters using the [utf8] option of inputenc.

Generally, however, the best way to deal with Unicode source (especially with non-latin scripts) is really XeLaTeX or LuaLaTeX.

There's an extended discussion of this here: Encoding remarks. See especially the comments by Philipp Lehman and Philipp Stephani.

Answer 2

In fact, utf8 may not be as restrictive as it seems: it only loads characters that can be displayed by the font encoding.

When typing

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

the font encoding is still OT1 when loading inputenc, which has very few characters. By using

\usepackage[T1]{fontenc} 
\usepackage[utf8]{inputenc}

you will allow all displayable utf8 characters to be available as input.

Answer 3

Don't use utf8x; with an up-to-date TeX distribution it could show necessary only for its most obscure features (faking characters with images from the Web, for instance).

The problem with Greek, which was probably the main reason for adopting utf8x instead of utf8, have since be solved and

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[polutonikogreek,english]{babel}
\begin{document}
This is english
\textgreek{Τηις ις γρεεκ}
This is english again.
\end{document}

will happily print

The occasional missing definitions can be coped with in a simple way. If you're able to input a Unicode character, such as the Welsh letters

Ââ Êê Îî Ôô Ŵŵ Ŷŷ Ïï

or the Latin vowels with prosodic marks

Ăă Ĕĕ Ĭĭ Ŏŏ Ŭŭ Āā Ēē Īī Ōō Ūū Ȳȳ

(y with breve is missing from Unicode, while a with breve is already defined by utf8 because it's a letter in Romanian), you can simply add the unknown ones to the list of known characters:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{newunicodechar}
% missing Welsh coverage
\newunicodechar{Ŵ}{^W}
\newunicodechar{ŵ}{^w}
\newunicodechar{Ŷ}{^Y}
\newunicodechar{ŷ}{^y}
% Latin vowels with prosodic marks

\newunicodechar{Ĕ}{\u{E}}
\newunicodechar{ĕ}{\u{e}}
\newunicodechar{Ĭ}{\u{I}}
\newunicodechar{ĭ}{\u{\i}}
\newunicodechar{Ŏ}{\u{O}}
\newunicodechar{ŏ}{\u{o}}
\newunicodechar{Ŭ}{\u{U}}
\newunicodechar{ŭ}{\u{u}}
\newunicodechar{Ā}{=A}
\newunicodechar{ā}{=a}
\newunicodechar{Ē}{=E}
\newunicodechar{ē}{=e}
\newunicodechar{Ī}{=I}
\newunicodechar{ī}{={\i}}
\newunicodechar{Ō}{=O}
\newunicodechar{ō}{=o}
\newunicodechar{Ū}{=U}
\newunicodechar{ū}{=u}
\newunicodechar{Ȳ}{=Y}
\newunicodechar{ȳ}{=y}
\begin{document}
Ââ Êê Îî Ôô Ŵŵ Ŷŷ Ïï
Ăă Ĕĕ Ĭĭ Ŏŏ Ŭŭ
Āā Ēē Īī Ōō Ūū Ȳȳ
\end{document}

Note that, for instance, the line

\newunicodechar{Ŵ}{\^W}

can be also input as

\DeclareUnicodeCharacter{0174}{\^W}

without the need of the newunicodechar package, because U+0174 is the code point of LATIN CAPITAL LETTER W WITH CIRCUMFLEX; but \newunicodechar frees from looking up in the Unicode tables.

---

Update, April 2016

With a recent LaTeX kernel almost none of the definitions above is necessary, because T1enc.dfu has been updated and enriched. Of the accented letters in the last example, only Ȳ and ȳ need to be defined (and they'll possibly be included in next releases).

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{newunicodechar}
\newunicodechar{Ȳ}{=Y}
\newunicodechar{ȳ}{=y}
\begin{document}
Ââ Êê Îî Ôô Ŵŵ Ŷŷ Ïï
Ăă Ĕĕ Ĭĭ Ŏŏ Ŭŭ
Āā Ēē Īī Ōō Ūū Ȳȳ
\end{document}

Update 2021

Now all those accented letters are defined in the kernel. So the following works out of the box. Note that \usepackage[T1]{fontenc} is not strictly required; however, loading it is better because it contains many precomposed accented letters.

\documentclass{article}
\usepackage[T1]{fontenc}
\begin{document}
Ââ Êê Îî Ôô Ŵŵ Ŷŷ Ïï
Ăă Ĕĕ Ĭĭ Ŏŏ Ŭŭ
Āā Ēē Īī Ōō Ūū Ȳȳ
\end{document}

Answer 4

"The simple answer is that utf8x is to be avoided if possible." Yes and No. No it's not so simple utf8x is sometimes necessary when you need to write greek or some special symbols. Yes utf8x is for a long time was unmaintained but we can use it. Try to compile the next code with utf8

\documentclass{article}

\usepackage[utf8x]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[polutonikogreek,english]{babel}

\renewcommand*{\textgreek}[1]{%
  \foreignlanguage{greek}{#1}%
}

\begin{document}

This is english
\textgreek{Τηις ις γρεεκ}
This is english again.

\end{document}

Answer 5

I've had the experience of not being able to compile Hebrew with utf8, only with utf8x, using pdflatex in MikTeX (e.g. 2.9). Many guides on writing Hebrew LaTeX suggest using utf8x:

• ivritex
• A Hebrew wikibook on LaTeX
• The Hebrew Wikipedia LaTeX article
• Yoav Goldberg' Hebrew LaTeX tips page at BGU
• etc.

This is not to contradict what the learned sages say above, it's just an example of a case in which it seems to be impossible to avoid (unless someone suggests a way like Ulrike's suggesting regarding Greek).

Note: This answer is only relevant to pdfTeX+Babel, not XeTeX+Polyglossia.

Answer 6

Update The utf8x option is no longer required.

The following now works unproblematically (except that certain characters are composed on-the-fly, but that's another matter).

\documentclass[welsh]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\begin{document}

 Ââ Êê Îî Ôô Ûû Ŵŵ Ŷŷ Ïï

\end{document}

Original answer

This answer is now deprecated and applies only for older installations. If your installation of TeX is current, you should not need utf8x any longer. utf8 should now be sufficient.

Welsh requires utf8x as the characters ŵ and ŷ are not recognised otherwise:

\documentclass[welsh]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8x]{inputenc}
\usepackage{babel}
\begin{document}

 Ââ Êê Îî Ôô Ŵŵ Ŷŷ Ïï

\end{document}

Obviously, XeLaTeX is an option although babel is still required as polyglossia doesn't support Welsh.

Answer 7

Just to point out another issue with utf8x, which I come across while digging through the documentation of the "historical" package inpmath: the kerning is "more likely" to be wrong.

%! TEX program = pdflatex
\documentclass{article}
% either...
\usepackage{ucs}
\usepackage[utf8x]{inputenc}
% or...
%\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
% unfortunately if the encoding is OT1 then the kerning will break for both package
\begin{document}
VÁ
V'A
\end{document}

In the first case only inputenc gives the correct kerning, ucs does not. In the second case you can see the correct kerning.

Output with ucs:

Output with inputenc:

The first row uses the Unicode character in the input directly, the second row uses the TeX command form \'A (which always work).

Normally fonts should set the kerning so that the gap between V and A are smaller, but the effect does not work in the ucs case as shown above.

The underlying reason is that utf8x executes some unexpandable command to process each Unicode character.