What is the CU file format?
A .cu file is a CUDA source code file - C/C++ extended with NVIDIA's parallel computing API for programming GPU accelerators. CUDA (Compute Unified Device Architecture) was introduced by NVIDIA in 2006 alongside the GeForce 8800 GTX and the first CUDA Toolkit.
.cu files are plain text and follow standard C/C++ syntax augmented with CUDA-specific qualifiers: __global__ marks a kernel function that runs on the GPU and is launched from the CPU; __device__ marks a function callable only from GPU code; __host__ marks an ordinary CPU function. Kernel launches use the triple-angle-bracket syntax <<<grid, block>>> to specify grid and thread-block dimensions, with built-in variables threadIdx, blockIdx, blockDim, and gridDim available inside kernels.
Compilation is handled by nvcc (NVIDIA CUDA Compiler Driver). It splits the .cu file in two passes: host C++ code goes to the system compiler (gcc/g++ on Linux, cl.exe on Windows), while device code compiles to PTX intermediate representation or binary .cubin for a specific GPU architecture. Header files with device-only declarations conventionally use the .cuh extension.
CUDA is NVIDIA-proprietary and requires an NVIDIA GPU. macOS support was dropped in CUDA 11.8 (2022). For cross-vendor GPU programming, alternatives include OpenCL (.cl files) and AMD HIP, which uses nearly identical syntax. The CUDA Toolkit is now at version 13.x (2026), and .cu files from CUDA 1.0 remain largely compatible with current toolchains.
Security & safety
RISK: LOWA .cu file is plain source code text; it cannot execute directly. Compiled CUDA binaries execute on the GPU and have the same risk profile as any compiled program from an untrusted source.
Format details
in a nutshell- Currency Exchange Rate File (various apps) - Some personal finance or point-of-sale applications use .cu for currency data files; plain text or binary, unrelated to NVIDIA.
Programs that open CU files
Windows5 apps
Microsoft Visual Studio
Freemium Install NVIDIA Nsight Visual Studio Edition plugin; provides CUDA IntelliSense and debugging. 
Notepad
Open-source Open for text viewing/editing; no CUDA-specific syntax highlighting by default (user-defined language files available). 
Visual Studio Code
Open-source Install the C/C++ or CUDA extension; open .cu file for syntax highlighting and IntelliSense. 
NVIDIA CUDA Toolkit (nvcc)
Free Compile with: nvcc myfile.cu -o myprogram. Requires NVIDIA GPU driver installed. 
Linux3 apps
Visual Studio Code
Open-source Install CUDA extension pack for syntax highlighting and Nsight integration. Technical details
deep spec| Encoding | Plain text, UTF-8 or ASCII |
| Compiler | nvcc (NVIDIA CUDA Compiler Driver) |
| GPU kernel qualifier | __global__ - GPU entry point, callable from CPU via <<<grid, block>>> syntax |
| Device function qualifier | __device__ - callable only from GPU code |
| Built-in variables | threadIdx, blockIdx, blockDim, gridDim (available inside kernels) |
| Compilation split | Host C++ to gcc/g++ (Linux) or cl.exe (Windows); device code to PTX or .cubin |
| Header extension | .cuh for files containing device-side declarations |
| Platform requirement | NVIDIA GPU required; macOS support dropped in CUDA 11.8 (2022) |
| Toolkit version range | CUDA 1.0 (2006) - CUDA 13.x (2026) |
| Output formats | PTX (portable IR) or .cubin (binary for specific GPU architecture) |
| Cross-vendor alternative | OpenCL (.cl) and AMD HIP for non-NVIDIA GPU targets |
| Typical file size | 1 KB - 500 KB (single kernel file) |
| Released | 2006 (CUDA 1.0) |
| Latest version | CUDA 13.x (2026); format co-evolves with the CUDA Toolkit |
| Specification | docs.nvidia.com |
CU conversions
Community Q&A
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