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A single-header ANSI C gui library
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This is a minimal state immediate mode graphical user interface toolkit written in ANSI C and licensed under public domain. It was designed as a simple embeddable user interface for application and does not have any dependencies, a default renderbackend or OS window and input handling but instead provides a very modular library approach by using simple input state for input and draw commands describing primitive shapes as output. So instead of providing a layered library that tries to abstract over a number of platform and render backends it only focuses on the actual UI.


  • Immediate mode graphical user interface toolkit
  • Single header library
  • Written in C89 (ANSI C)
  • Small codebase (~18kLOC)
  • Focus on portability, efficiency and simplicity
  • No dependencies (not even the standard library if not wanted)
  • Fully skinnable and customizable
  • Low memory footprint with total memory control if needed or wanted
  • UTF-8 support
  • No global or hidden state
  • Customizable library modules (you can compile and use only what you need)
  • Optional font baker and vertex buffer output


This library is self contained in one single header file and can be used either in header only mode or in implementation mode. The header only mode is used by default when included and allows including this header in other headers and does not contain the actual implementation.

The implementation mode requires to define the preprocessor macro NK_IMPLEMENTATION in one .c/.cpp file before #includeing this file, e.g.:

#include "nuklear.h"

IMPORTANT: Every time you include "nuklear.h" you have to define the same optional flags. This is very important not doing it either leads to compiler errors or even worse stack corruptions.


screenshot screen screen2 node skinning gamepad


/* init gui state */
struct nk_context ctx;
nk_init_fixed(&ctx, calloc(1, MAX_MEMORY), MAX_MEMORY, &font);

enum {EASY, HARD};
static int op = EASY;
static float value = 0.6f;
static int i =  20;

if (nk_begin(&ctx, "Show", nk_rect(50, 50, 220, 220),
    /* fixed widget pixel width */
    nk_layout_row_static(&ctx, 30, 80, 1);
    if (nk_button_label(&ctx, "button")) {
        /* event handling */

    /* fixed widget window ratio width */
    nk_layout_row_dynamic(&ctx, 30, 2);
    if (nk_option_label(&ctx, "easy", op == EASY)) op = EASY;
    if (nk_option_label(&ctx, "hard", op == HARD)) op = HARD;

    /* custom widget pixel width */
    nk_layout_row_begin(&ctx, NK_STATIC, 30, 2);
        nk_layout_row_push(&ctx, 50);
        nk_label(&ctx, "Volume:", NK_TEXT_LEFT);
        nk_layout_row_push(&ctx, 110);
        nk_slider_float(&ctx, 0, &value, 1.0f, 0.1f);



There are a number of nuklear bindings for different languges created by other authors. I cannot atest for their quality since I am not necessarily proficient in either of these languages. Furthermore there are no guarantee that all bindings will always be kept up to date:


Developed by Micha Mettke and every direct or indirect contributor to the GitHub.

Embeds stb_texedit, stb_truetype and stb_rectpack by Sean Barret (public domain)
Embeds ProggyClean.ttf font by Tristan Grimmer (MIT license).

Big thank you to Omar Cornut (ocornut@github) for his imgui library and giving me the inspiration for this library, Casey Muratori for handmade hero and his original immediate mode graphical user interface idea and Sean Barret for his amazing single header libraries which restored my faith in libraries and brought me to create some of my own.


This software is dual-licensed to the public domain and under the following license: you are granted a perpetual, irrevocable license to copy, modify, publish and distribute this file as you see fit.

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