libgrapheme is an extremely simple C99 library providing utilities for properly handling Unicode strings made up of user-perceived characters ('grapheme clusters') according to the Unicode standard. While providing convenience functions to operate on UTF-8-encoded strings, you can also use libgrapheme for any other encoding as well.

The necessary lookup-tables and test-data are automatically generated from the Unicode standard data, ensuring correctness and validation. A specialized 'Heisenstate' state-handling combined with O(log(n))-binary-search on the lookup-tables and data-recycling provides great processing-performance in the order of millions of codepoints per second.

There is no complicated build-system involved and it's all done using one POSIX-compliant Makefile. All you need is a C99 compiler, because the data-generators are also written in C99.


The goal of this project is to be a suckless and statically linkable alternative to the existing bloated, complicated and overscoped solutions for Unicode string handling (ICU, GNU's libunistring, etc.), motivating more hackers to properly handle Unicode strings in their projects and allowing this even in embedded applications.

The problem can be easily seen when looking at the sizes of the respective libraries: The ICU library (libicudata.a, libicui18n.a, libicuio.a, libicutest.a, libicutu.a, libicuuc.a) is around 38MB and libunistring (libunistring.a) is around 2MB, which is unacceptable for static linking. Both take many minutes to compile even on a good computer and require a lot of dependencies, including Python for ICU. On the other hand libgrapheme (libgrapheme.a) only weighs in at around 40K and is compiled (including Unicode data parsing) in fractions of a second, requiring nothing but a C99 compiler and make(1).

While ICU and libunistring offer a lot of functions and the weight mostly comes from locale-data provided by the Unicode standard, which is applied implementation-specifically (!) for some things, the same standard always defines a sane 'default' behaviour as an alternative in such cases that is satisfying in 99% of the cases and which you can rely on.

For some languages, for instance, it is necessary to have a dictionary on hand to always accurately determine when a word begins and ends. The defaults provided by the standard, though, already do a good job respecting the language's boundaries in the general case and are not too taxing in terms of performance.

Handling user-perceived characters is not locale-dependent, though, and does not require locale-data.

Getting Started

Installing libgrapheme will install the header grapheme.h and both the static library libgrapheme.a and the dynamic library in the respective folders. Access the manual under libgrapheme(7) by typing

man libgrapheme

and looking at the referred pages, e.g. grapheme_next_character_break(3). Each page contains code-examples and an extensive description. To give one example that is also given in the manuals, the following code separates a given string 'Tëst 👨‍👩‍👦 🇺🇸 नी நி!' into its user-perceived characters:

#include <grapheme.h>
#include <stdint.h>
#include <stdio.h>

	/* UTF-8 encoded input */
	char *s = "T\xC3\xABst \xF0\x9F\x91\xA8\xE2\x80\x8D\xF0"
	          "\x9F\x91\xA9\xE2\x80\x8D\xF0\x9F\x91\xA6 \xF0"
	          "\x9F\x87\xBA\xF0\x9F\x87\xB8 \xE0\xA4\xA8\xE0"
	          "\xA5\x80 \xE0\xAE\xA8\xE0\xAE\xBF!";
	size_t ret, off;

	printf("Input: \"%s\"\n", s);

	for (off = 0; s[off] != '\0'; off += ret) {
		ret = grapheme_next_character_break(s + off, SIZE_MAX);
		printf("%2zu bytes | %.*s\n", ret, (int)ret, s + off, ret);

	return 0;

This code can be compiled with

cc (-static) -o example example.c -lgrapheme

and the output is

Input: "Tëst 👨‍👩‍👦 🇺🇸 नी நி!"
 1 bytes | T
 2 bytes | ë
 1 bytes | s
 1 bytes | t
 1 bytes |  
18 bytes | 👨‍👩‍👦
 1 bytes |  
 8 bytes | 🇺🇸
 1 bytes |  
 6 bytes | नी
 1 bytes |  
 6 bytes | நி
 1 bytes | !


You can browse the source code repository or get a copy with the following command:

git clone



Please contact me if you find information that could be added to this page.