Ultralight

GLFW is an open-source, multi-platform library designed for OpenGL, OpenGL ES, and Vulkan application development. It provides a platform-independent API for:

• Creating windows, contexts, and surfaces
• Reading input
• Handling events

Supported platforms include Windows, macOS, and Linux/Unix-like systems. Experimental support is available for the Wayland protocol and the Mir display server.

Ultralight uses a dual-licensing model:

• Free License:
  • For non-commercial use.
  • For commercial use by indie companies with < $100K annual revenue.
  • Includes the full SDK.
• Commercial License:
  • Required for larger commercial entities.
  • Includes performance tools, extra configurations, and source code.
  • Contact the team for enterprise licensing and volume discounts.

Ultralight provides two distinct rendering paths depending on your integration needs:

CPU Renderer

• Best for: Fast, lightweight, and easy integration.
• Output: Renders to a 32-bit BGRA pixel buffer.
• Technology: Based on Skia, accelerated via multi-threaded SIMD.
• Reference: See the Game Integration Guide.

GPU Renderer

• Best for: High-performance, customizable, and portable applications requiring high animation performance.
• Output: Renders directly to a GPU texture.
• Technology: Accelerated via tesselated geometry and pixel shaders.
• Reference: See Using a Custom GPUDriver.

Ultralight offers different integration paths based on your target application type:

For Game Developers

Designed for high-performance web-content in game engine environments. You can choose between the CPU renderer for reliability or the GPU renderer for animation performance.

• Guide: Game Integration Guide

For Desktop-App Developers

Allows you to build front-ends with HTML/CSS/JS while using C/C++ for logic. You can either:

1. Embed the renderer directly within your existing run loop.
2. Use AppCore, an optional desktop app runtime that provides convenient native window management and accelerated rendering.

• Guide: Desktop App Guide

When reporting unexpected run-time behavior, first set an error callback to identify the cause. If the library is crashing or triggering asserts, verify that all object handles and pointers are valid.

Guidelines for bug reports:

• Provide a short, self-contained code example inline if possible.
• Provide all information as text, not images (use triple backticks for code blocks).
• Use issue labels for platforms and GPU manufacturers instead of including them in the subject line.

Note that window moving/resizing by a user may block the main thread on some platforms; use a refresh callback to keep contents updated. For X11 users, please include your desktop environment (GNOME, KDE, etc.) and window manager.

Use the events tool (found in tests/events.c in the source tree) to print all information provided to every GLFW callback. Include this output in your report.

Include the following in your report:

• OS and version
• GLFW release version or commit ID
• Error messages from the error callback
• The output of the events tool.
• If using a Virtual Machine, include the VM name and version.

Use the following template:

OS and version:
Release or commit:
Error messages:
events output:

Before reporting, check the Compiling GLFW and Building applications guides. Many issues stem from missing system libraries or linker flags, especially when using GLFW as a static library.

Use the following template for your report:

OS and version:
Compiler version:
Release or commit:
Build log:

The latest SDKs are available for download for Windows, Linux, and macOS (x64). For console platforms like Xbox, PS4, and PS5, you must contact the Ultralight team directly.

• Windows (x64): Download
• Linux (x64): Download
• macOS (x64): Download

GLFW can be compiled on various platforms using the following compilers:

• Windows: Visual C++ 2010 and later, MinGW, and MinGW-w64.
• macOS: Clang.
• Linux/Unix-like: GCC and Clang.

GLFW only requires the headers and libraries for your window system; it does not require headers for context creation APIs (WGL, GLX, EGL, NSGL, OSMesa) or rendering APIs (OpenGL, OpenGL ES, Vulkan) to enable support for them.

Pre-compiled Windows binaries are available for all supported compilers via the official GLFW downloads page.

Note that on some headless systems, glfwGetPrimaryMonitor may return NULL. Additionally, GLFW only reports video modes approved by the OS; this is intended behavior.

Use the monitors tool (found in tests/monitors.c in the source tree) to list all information GLFW provides about detected monitors. Include this output in your report.

Include the following in your report:

• OS and version
• GLFW release version or commit ID
• Error messages from the error callback
• The output of the monitors tool.
• If using a Virtual Machine, include the VM name and version.

Use the following template:

OS and version:
Release or commit:
Error messages:
monitors output: