Text run is not in Unicode Normalization Form C

Question

While I was trying to validate my site I get the following error:

Text run is not in Unicode Normalization Form C

A: Wh

Answer 1

What does it mean?

From W3C:

In Unicode it is possible to produce the same text with different sequences of characters. For example, take the Hungarian word világ. The fourth letter could be stored in memory as a precomposed U+00E1 LATIN SMALL LETTER A WITH ACUTE (a single character) or as a decomposed sequence of U+0061 LATIN SMALL LETTER A followed by U+0301 COMBINING ACUTE ACCENT (two characters).

világ = világ

The Unicode Standard allows either of these alternatives, but requires that both be treated as identical. To improve efficiency, an application will usually normalize text before performing searches or comparisons. Normalization, in this case, means converting the text to use all precomposed or all decomposed characters.

There are four normalization forms specified by the Unicode Standard: NFC, NFD, NFKC and NFKD. The C stands for (pre-)composed, and the D for decomposed. The K stands for compatibility. To improve interoperability, the W3C recommends the use of NFC normalized text on the Web.

Besides "to improve interoperability", precomposed text usually looks better than decomposes text.

How can I fix this with free tools

By using the function equivalent to Python's text = unicodedata.normalize('NFC', text) in your favorite programming language.

(Or, if you weren't planning to write a program, your question should be moved to superuser or webmasters.)