YoloDotNet v4.0

YoloDotNet is a blazing-fast, fully featured C# library for real-time object detection, OBB, segmentation, classification, pose estimation — and tracking — using YOLOv5u–v12, YOLO-World, and YOLO-E models.

Built on .NET 8 and powered by ONNX Runtime, YoloDotNet delivers high-performance inference on Windows, Linux, and macOS, using pluggable execution providers including CPU, CUDA / TensorRT, OpenVINO, and CoreML.

Designed for both flexibility and speed, YoloDotNet supports image and video processing out of the box, including live streams, frame skipping, and fully customizable visualizations.

Execution Providers:

See the table below to choose the right one for your platform.

Supported Tasks:

Classification	Object Detection	OBB Detection	Segmentation	Pose Estimation
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📖 Table of Contents

• What's new in v4.0
• Requirements
  • ONNX Model (opset 17)
  • Installation
• Customization
• Support YoloDotNet
• License

🚀 YoloDotNet v4.0 — Modular Execution, Maximum Performance

ℹ️ Breaking Change (v4.0)
YoloDotNet v4.0 introduces a new modular architecture and is therefore a breaking update.

The core YoloDotNet package is now completely execution-provider agnostic and no longer ships with any ONNX Runtime dependencies.
Execution providers (CPU, CUDA, OpenVINO, CoreML, etc.) are now separate NuGet packages and must be referenced explicitly.

What this means for you:

• You must install YoloDotNet and exactly one execution provider
• Execution provider selection and configuration code has changed
• Existing projects upgrading from v3.x will need to update their NuGet references and setup code
• The inference API remains familiar, but provider wiring is now explicit and platform-aware

The upside? Cleaner architecture, fewer native dependency conflicts, and a setup that behaves consistently across platforms.

What's new

• ✅ Fully modular execution providers
  Execution providers have officially moved out and got their own place. YoloDotNet Core now focuses on what to run, not how to run it — leaving all the platform-specific heavy lifting to dedicated NuGet packages. The result? Cleaner projects, fewer native dependency tantrums, and behavior you can actually predict.

• ✅ New execution providers: OpenVINO & CoreML
  Two shiny new execution providers join the lineup:

  • Intel OpenVINO — Squeezes the most out of Intel CPUs and iGPUs on Windows and Linux
  • Apple CoreML — Taps directly into Apple’s native ML stack for fast, hardware-accelerated inference on macOS Plug them in, run inference, enjoy the speed — no code changes, no drama.

• ✅ Improved CUDA execution provider
  Smarter and more explicit GPU handling for CUDA and TensorRT, so your NVIDIA hardware does what you expect — and not what it feels like doing today.

• ✅ Grayscale ONNX model support
  Run inference on grayscale-only models when color is just wasted effort. Less data, less work, same results — because sometimes black and white is all you need.

• 🔄 Dependency updates

  • SkiaSharp updated to 3.119.1
  • ONNX Runtime (CUDA) updated to 1.23.2
    Fresh bits, fewer bugs, better vibes.

Requirements

To use YoloDotNet, you need:

• A YOLO model exported to ONNX format (opset 17)
• The YoloDotNet core NuGet package
• Exactly one execution provider package suitable for your target platform

ONNX Model (opset 17)

All models — including custom-trained models — must be exported to ONNX format with opset 17 for best performance and compatibility.

For instructions on exporting YOLO models to ONNX, see:
https://docs.ultralytics.com/modes/export/#usage-examples

Note: Dynamic models are not supported.

Installation

1. Install YoloDotNet Core

   dotnet add package YoloDotNet

2. Select an Execution Provider

   Execution Provider	Windows	Linux	macOS	Documentation
   CPU	✅	✅	✅	CPU README
   CUDA / TensorRT	✅	✅	❌	CUDA README
   OpenVINO	✅	✅	❌	OpenVINO README
   CoreML	❌	❌	✅	CoreML README

   ℹ️ Important limitation
   Only one execution provider package may be referenced.
   Execution providers ship their own ONNX Runtime native binaries, and mixing providers will overwrite shared DLLs and cause runtime errors.

🚀 Quick Start: Dive into the Demos

Can’t wait to see YoloDotNet in action? The demo projects are the fastest way to get started and explore everything this library can do.

Each demo showcases:

• Classification
• Object Detection
• OBB Detection
• Segmentation
• Pose Estimation

Oh, and it doesn’t stop there — there’s a demo for real-time video inference too! Whether you’re analyzing local video files or streaming live, the demos have you covered.

Each demo is packed with inline comments to help you understand how everything works under the hood. From model setup, execution provider, preprocessing to video streaming and result rendering — it's all there.

Pro tip: For detailed configuration options and usage guidance, check out the comments in the demo source files.

Open the YoloDotNet.Demo projects, build, run, and start detecting like a pro. ✨

Bare Minimum — Get Up and Running in a Snap

Sometimes you just want to see the magic happen without the bells and whistles. Here’s the absolute simplest way to load a model, run inference on an image, and get your detected objects:

using SkiaSharp;
using YoloDotNet;
using YoloDotNet.Enums;
using YoloDotNet.Models;
using YoloDotNet.Extensions;
using YoloDotNet.ExecutionProvider.Cpu;

public class Program
{
    // ⚠️ Note: The accuracy of inference results depends heavily on how you configure preprocessing and thresholds.
    // Make sure to read the README section "Accuracy Depends on Configuration":
    // https://github.com/NickSwardh/YoloDotNet/tree/master#%EF%B8%8F-accuracy-depends-on-configuration

    static void Main(string[] args)
    {
        // Instantiate yolo
        using var yolo = new Yolo(new YoloOptions
        {
            // Select an execution provider for your target system
            // 
            ExecutionProvider = new CpuExecutionProvider(model: "path/to/model.onnx"),

            // ...other options here
        });

        // Load image
        using var image = SKBitmap.Decode("image.jpg");

        // Run inference
        var results = yolo.RunObjectDetection(image, confidence: 0.25, iou: 0.7);

        image.Draw(results);         // Draw boxes and labels
        image.Save("result.jpg");    // Save – boom, done!
    }
}

That’s it! No fuss.

Of course, the real power lies in customizing the pipeline, streaming images/videos, or tweaking models… but this snippet gets you started in seconds.

Want more? Dive into the demos and source code for full examples, from video streams to segmentation and pose estimation.

⚠️ Accuracy Depends on Configuration

The accuracy of your results depends heavily on how you configure preprocessing and thresholds. Even with a correctly trained model, mismatched settings can cause accuracy loss. There is no one-size-fits-all configuration — optimal values depend on your dataset, how your model was trained, and your specific application needs.

🔑 Key Factors

1. Image Preprocessing & Resize Mode
   • Controlled via ImageResize.
   • Must match the preprocessing used during training to ensure accurate detections.

     Proportional dataset	Stretched dataset
     Use ImageResize.Proportional (default) if the dataset images were not distorted during training and their aspect ratio was preserved.	Use ImageResize.Stretched if the dataset images were resized directly to the model’s input size (e.g., 640x640), ignoring the original aspect ratio.

   • Important: Selecting the wrong resize mode can reduce detection accuracy.
2. Sampling Options
   • Controlled via SamplingOptions.
   • Define how pixel data is resampled when resizing (e.g., Cubic, NearestNeighbor, Bilinear). This choice has a direct impact on the accuracy of your detections, as different resampling methods can slightly alter object shapes and edges.
   • YoloDotNet default:

     SamplingOptions = new SKSamplingOptions(SKFilterMode.Nearest, SKMipmapMode.None);

     💡 Tip: Check the ResizeImage Benchmarks for examples of different SamplingOptions and to help you choose the best settings for your needs.
3. Confidence & IoU Thresholds
   • Results are filtered based on thresholds you set during inference:
     • Confidence → Minimum probability for a detection to count.
     • IoU (Intersection-over-Union) → Overlap required to merge/suppress detections.
   • Too low → more false positives.
   • Too high → more missed detections.
   • Fine-tune these values for your dataset and application.

💡 Tip: Start with the defaults, then adjust ImageResize, SamplingOptions, and Confidence/IoU thresholds based on your dataset for optimal detection results.

Make It Yours – Customize the Look

Want to give your detections a personal touch? Go ahead! If you're drawing bounding boxes on-screen, there’s full flexibility to style them just the way you like:

• Custom Colors – Use the built-in class-specific colors or define your own for every bounding box.
• Font Style & Size – Choose your favorite font, set the size, and even change the color for the labels.
• Custom Fonts – Yep, you can load your own font files to give your overlay a totally unique feel.

If that's not enough, check out the extension methods in the main YoloDotNet repository — a solid boilerplate for building even deeper customizations tailored exactly to your needs.

For practical examples on drawing and customization, don’t forget to peek at the demo project source code too!

Support YoloDotNet

YoloDotNet is the result of countless hours of development, testing, and continuous improvement — all offered freely to the community.

If you’ve found my project helpful, consider supporting its development. Your contribution helps cover the time and resources needed to keep the project maintained, updated, and freely available to everyone.

Support the project:

Whether it's a donation, sponsorship, or just spreading the word — every bit of support fuels the journey. Thank you for helping YoloDotNet grow! ❤️

References & Acknowledgements

https://github.com/ultralytics/ultralytics
https://github.com/sstainba/Yolov8.Net
https://github.com/mentalstack/yolov5-net

License

YoloDotNet is © 2023–2025 Niklas Swärd (GitHub)
Licensed under the GNU General Public License v3.0 or later.

See the LICENSE file for the full license text.

This software is provided “as is”, without warranty of any kind.
The author is not liable for any damages arising from its use.