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YOLO settings and hyperparameters play a critical role in the model's performance, speed, and accuracy. These settings and hyperparameters can affect the model's behavior at various stages of the model development process, including training, validation, and prediction.

Watch: Mastering Ultralytics YOLOv8: Configuration

Ultralytics commands use the following syntax:


from ultralytics import YOLO

# Load a YOLOv8 model from a pre-trained weights file
model = YOLO("")

# Run MODE mode using the custom arguments ARGS (guess TASK)


Default ARG values are defined on this page from the cfg/defaults.yaml file.


YOLO models can be used for a variety of tasks, including detection, segmentation, classification and pose. These tasks differ in the type of output they produce and the specific problem they are designed to solve.

  • Detect: For identifying and localizing objects or regions of interest in an image or video.
  • Segment: For dividing an image or video into regions or pixels that correspond to different objects or classes.
  • Classify: For predicting the class label of an input image.
  • Pose: For identifying objects and estimating their keypoints in an image or video.
  • OBB: Oriented (i.e. rotated) bounding boxes suitable for satellite or medical imagery.
Argument Default Description
task 'detect' Specifies the YOLO task to be executed. Options include detect for object detection, segment for segmentation, classify for classification, pose for pose estimation and OBB for oriented bounding boxes. Each task is tailored to specific types of output and problems within image and video analysis.

Tasks Guide


YOLO models can be used in different modes depending on the specific problem you are trying to solve. These modes include:

  • Train: For training a YOLOv8 model on a custom dataset.
  • Val: For validating a YOLOv8 model after it has been trained.
  • Predict: For making predictions using a trained YOLOv8 model on new images or videos.
  • Export: For exporting a YOLOv8 model to a format that can be used for deployment.
  • Track: For tracking objects in real-time using a YOLOv8 model.
  • Benchmark: For benchmarking YOLOv8 exports (ONNX, TensorRT, etc.) speed and accuracy.
Argument Default Description
mode 'train' Specifies the mode in which the YOLO model operates. Options are train for model training, val for validation, predict for inference on new data, export for model conversion to deployment formats, track for object tracking, and benchmark for performance evaluation. Each mode is designed for different stages of the model lifecycle, from development through deployment.

Modes Guide

Train Settings

The training settings for YOLO models encompass various hyperparameters and configurations used during the training process. These settings influence the model's performance, speed, and accuracy. Key training settings include batch size, learning rate, momentum, and weight decay. Additionally, the choice of optimizer, loss function, and training dataset composition can impact the training process. Careful tuning and experimentation with these settings are crucial for optimizing performance.

Argument Default Description
model None Specifies the model file for training. Accepts a path to either a .pt pretrained model or a .yaml configuration file. Essential for defining the model structure or initializing weights.
data None Path to the dataset configuration file (e.g., coco8.yaml). This file contains dataset-specific parameters, including paths to training and validation data, class names, and number of classes.
epochs 100 Total number of training epochs. Each epoch represents a full pass over the entire dataset. Adjusting this value can affect training duration and model performance.
time None Maximum training time in hours. If set, this overrides the epochs argument, allowing training to automatically stop after the specified duration. Useful for time-constrained training scenarios.
patience 100 Number of epochs to wait without improvement in validation metrics before early stopping the training. Helps prevent overfitting by stopping training when performance plateaus.
batch 16 Batch size, with three modes: set as an integer (e.g., batch=16), auto mode for 60% GPU memory utilization (batch=-1), or auto mode with specified utilization fraction (batch=0.70).
imgsz 640 Target image size for training. All images are resized to this dimension before being fed into the model. Affects model accuracy and computational complexity.
save True Enables saving of training checkpoints and final model weights. Useful for resuming training or model deployment.
save_period -1 Frequency of saving model checkpoints, specified in epochs. A value of -1 disables this feature. Useful for saving interim models during long training sessions.
cache False Enables caching of dataset images in memory (True/ram), on disk (disk), or disables it (False). Improves training speed by reducing disk I/O at the cost of increased memory usage.
device None Specifies the computational device(s) for training: a single GPU (device=0), multiple GPUs (device=0,1), CPU (device=cpu), or MPS for Apple silicon (device=mps).
workers 8 Number of worker threads for data loading (per RANK if Multi-GPU training). Influences the speed of data preprocessing and feeding into the model, especially useful in multi-GPU setups.
project None Name of the project directory where training outputs are saved. Allows for organized storage of different experiments.
name None Name of the training run. Used for creating a subdirectory within the project folder, where training logs and outputs are stored.
exist_ok False If True, allows overwriting of an existing project/name directory. Useful for iterative experimentation without needing to manually clear previous outputs.
pretrained True Determines whether to start training from a pretrained model. Can be a boolean value or a string path to a specific model from which to load weights. Enhances training efficiency and model performance.
optimizer 'auto' Choice of optimizer for training. Options include SGD, Adam, AdamW, NAdam, RAdam, RMSProp etc., or auto for automatic selection based on model configuration. Affects convergence speed and stability.
verbose False Enables verbose output during training, providing detailed logs and progress updates. Useful for debugging and closely monitoring the training process.
seed 0 Sets the random seed for training, ensuring reproducibility of results across runs with the same configurations.
deterministic True Forces deterministic algorithm use, ensuring reproducibility but may affect performance and speed due to the restriction on non-deterministic algorithms.
single_cls False Treats all classes in multi-class datasets as a single class during training. Useful for binary classification tasks or when focusing on object presence rather than classification.
rect False Enables rectangular training, optimizing batch composition for minimal padding. Can improve efficiency and speed but may affect model accuracy.
cos_lr False Utilizes a cosine learning rate scheduler, adjusting the learning rate following a cosine curve over epochs. Helps in managing learning rate for better convergence.
close_mosaic 10 Disables mosaic data augmentation in the last N epochs to stabilize training before completion. Setting to 0 disables this feature.
resume False Resumes training from the last saved checkpoint. Automatically loads model weights, optimizer state, and epoch count, continuing training seamlessly.
amp True Enables Automatic Mixed Precision (AMP) training, reducing memory usage and possibly speeding up training with minimal impact on accuracy.
fraction 1.0 Specifies the fraction of the dataset to use for training. Allows for training on a subset of the full dataset, useful for experiments or when resources are limited.
profile False Enables profiling of ONNX and TensorRT speeds during training, useful for optimizing model deployment.
freeze None Freezes the first N layers of the model or specified layers by index, reducing the number of trainable parameters. Useful for fine-tuning or transfer learning.
lr0 0.01 Initial learning rate (i.e. SGD=1E-2, Adam=1E-3) . Adjusting this value is crucial for the optimization process, influencing how rapidly model weights are updated.
lrf 0.01 Final learning rate as a fraction of the initial rate = (lr0 * lrf), used in conjunction with schedulers to adjust the learning rate over time.
momentum 0.937 Momentum factor for SGD or beta1 for Adam optimizers, influencing the incorporation of past gradients in the current update.
weight_decay 0.0005 L2 regularization term, penalizing large weights to prevent overfitting.
warmup_epochs 3.0 Number of epochs for learning rate warmup, gradually increasing the learning rate from a low value to the initial learning rate to stabilize training early on.
warmup_momentum 0.8 Initial momentum for warmup phase, gradually adjusting to the set momentum over the warmup period.
warmup_bias_lr 0.1 Learning rate for bias parameters during the warmup phase, helping stabilize model training in the initial epochs.
box 7.5 Weight of the box loss component in the loss function, influencing how much emphasis is placed on accurately predicting bounding box coordinates.
cls 0.5 Weight of the classification loss in the total loss function, affecting the importance of correct class prediction relative to other components.
dfl 1.5 Weight of the distribution focal loss, used in certain YOLO versions for fine-grained classification.
pose 12.0 Weight of the pose loss in models trained for pose estimation, influencing the emphasis on accurately predicting pose keypoints.
kobj 2.0 Weight of the keypoint objectness loss in pose estimation models, balancing detection confidence with pose accuracy.
label_smoothing 0.0 Applies label smoothing, softening hard labels to a mix of the target label and a uniform distribution over labels, can improve generalization.
nbs 64 Nominal batch size for normalization of loss.
overlap_mask True Determines whether segmentation masks should overlap during training, applicable in instance segmentation tasks.
mask_ratio 4 Downsample ratio for segmentation masks, affecting the resolution of masks used during training.
dropout 0.0 Dropout rate for regularization in classification tasks, preventing overfitting by randomly omitting units during training.
val True Enables validation during training, allowing for periodic evaluation of model performance on a separate dataset.
plots False Generates and saves plots of training and validation metrics, as well as prediction examples, providing visual insights into model performance and learning progression.

Note on Batch-size Settings

The batch argument can be configured in three ways:

  • Fixed Batch Size: Set an integer value (e.g., batch=16), specifying the number of images per batch directly.
  • Auto Mode (60% GPU Memory): Use batch=-1 to automatically adjust batch size for approximately 60% CUDA memory utilization.
  • Auto Mode with Utilization Fraction: Set a fraction value (e.g., batch=0.70) to adjust batch size based on the specified fraction of GPU memory usage.

Train Guide

Predict Settings

The prediction settings for YOLO models encompass a range of hyperparameters and configurations that influence the model's performance, speed, and accuracy during inference on new data. Careful tuning and experimentation with these settings are essential to achieve optimal performance for a specific task. Key settings include the confidence threshold, Non-Maximum Suppression (NMS) threshold, and the number of classes considered. Additional factors affecting the prediction process are input data size and format, the presence of supplementary features such as masks or multiple labels per box, and the particular task the model is employed for.

Inference arguments:

Argument Type Default Description
source str 'ultralytics/assets' Specifies the data source for inference. Can be an image path, video file, directory, URL, or device ID for live feeds. Supports a wide range of formats and sources, enabling flexible application across different types of input.
conf float 0.25 Sets the minimum confidence threshold for detections. Objects detected with confidence below this threshold will be disregarded. Adjusting this value can help reduce false positives.
iou float 0.7 Intersection Over Union (IoU) threshold for Non-Maximum Suppression (NMS). Lower values result in fewer detections by eliminating overlapping boxes, useful for reducing duplicates.
imgsz int or tuple 640 Defines the image size for inference. Can be a single integer 640 for square resizing or a (height, width) tuple. Proper sizing can improve detection accuracy and processing speed.
half bool False Enables half-precision (FP16) inference, which can speed up model inference on supported GPUs with minimal impact on accuracy.
device str None Specifies the device for inference (e.g., cpu, cuda:0 or 0). Allows users to select between CPU, a specific GPU, or other compute devices for model execution.
max_det int 300 Maximum number of detections allowed per image. Limits the total number of objects the model can detect in a single inference, preventing excessive outputs in dense scenes.
vid_stride int 1 Frame stride for video inputs. Allows skipping frames in videos to speed up processing at the cost of temporal resolution. A value of 1 processes every frame, higher values skip frames.
stream_buffer bool False Determines if all frames should be buffered when processing video streams (True), or if the model should return the most recent frame (False). Useful for real-time applications.
visualize bool False Activates visualization of model features during inference, providing insights into what the model is "seeing". Useful for debugging and model interpretation.
augment bool False Enables test-time augmentation (TTA) for predictions, potentially improving detection robustness at the cost of inference speed.
agnostic_nms bool False Enables class-agnostic Non-Maximum Suppression (NMS), which merges overlapping boxes of different classes. Useful in multi-class detection scenarios where class overlap is common.
classes list[int] None Filters predictions to a set of class IDs. Only detections belonging to the specified classes will be returned. Useful for focusing on relevant objects in multi-class detection tasks.
retina_masks bool False Uses high-resolution segmentation masks if available in the model. This can enhance mask quality for segmentation tasks, providing finer detail.
embed list[int] None Specifies the layers from which to extract feature vectors or embeddings. Useful for downstream tasks like clustering or similarity search.

Visualization arguments:

Argument Type Default Description
show bool False If True, displays the annotated images or videos in a window. Useful for immediate visual feedback during development or testing.
save bool False Enables saving of the annotated images or videos to file. Useful for documentation, further analysis, or sharing results.
save_frames bool False When processing videos, saves individual frames as images. Useful for extracting specific frames or for detailed frame-by-frame analysis.
save_txt bool False Saves detection results in a text file, following the format [class] [x_center] [y_center] [width] [height] [confidence]. Useful for integration with other analysis tools.
save_conf bool False Includes confidence scores in the saved text files. Enhances the detail available for post-processing and analysis.
save_crop bool False Saves cropped images of detections. Useful for dataset augmentation, analysis, or creating focused datasets for specific objects.
show_labels bool True Displays labels for each detection in the visual output. Provides immediate understanding of detected objects.
show_conf bool True Displays the confidence score for each detection alongside the label. Gives insight into the model's certainty for each detection.
show_boxes bool True Draws bounding boxes around detected objects. Essential for visual identification and location of objects in images or video frames.
line_width None or int None Specifies the line width of bounding boxes. If None, the line width is automatically adjusted based on the image size. Provides visual customization for clarity.

Predict Guide

Validation Settings

The val (validation) settings for YOLO models involve various hyperparameters and configurations used to evaluate the model's performance on a validation dataset. These settings influence the model's performance, speed, and accuracy. Common YOLO validation settings include batch size, validation frequency during training, and performance evaluation metrics. Other factors affecting the validation process include the validation dataset's size and composition, as well as the specific task the model is employed for.

Argument Type Default Description
data str None Specifies the path to the dataset configuration file (e.g., coco8.yaml). This file includes paths to validation data, class names, and number of classes.
imgsz int 640 Defines the size of input images. All images are resized to this dimension before processing.
batch int 16 Sets the number of images per batch. Use -1 for AutoBatch, which automatically adjusts based on GPU memory availability.
save_json bool False If True, saves the results to a JSON file for further analysis or integration with other tools.
save_hybrid bool False If True, saves a hybrid version of labels that combines original annotations with additional model predictions.
conf float 0.001 Sets the minimum confidence threshold for detections. Detections with confidence below this threshold are discarded.
iou float 0.6 Sets the Intersection Over Union (IoU) threshold for Non-Maximum Suppression (NMS). Helps in reducing duplicate detections.
max_det int 300 Limits the maximum number of detections per image. Useful in dense scenes to prevent excessive detections.
half bool True Enables half-precision (FP16) computation, reducing memory usage and potentially increasing speed with minimal impact on accuracy.
device str None Specifies the device for validation (cpu, cuda:0, etc.). Allows flexibility in utilizing CPU or GPU resources.
dnn bool False If True, uses the OpenCV DNN module for ONNX model inference, offering an alternative to PyTorch inference methods.
plots bool False When set to True, generates and saves plots of predictions versus ground truth for visual evaluation of the model's performance.
rect bool False If True, uses rectangular inference for batching, reducing padding and potentially increasing speed and efficiency.
split str val Determines the dataset split to use for validation (val, test, or train). Allows flexibility in choosing the data segment for performance evaluation.

Careful tuning and experimentation with these settings are crucial to ensure optimal performance on the validation dataset and detect and prevent overfitting.

Val Guide

Export Settings

Export settings for YOLO models encompass configurations and options related to saving or exporting the model for use in different environments or platforms. These settings can impact the model's performance, size, and compatibility with various systems. Key export settings include the exported model file format (e.g., ONNX, TensorFlow SavedModel), the target device (e.g., CPU, GPU), and additional features such as masks or multiple labels per box. The export process may also be affected by the model's specific task and the requirements or constraints of the destination environment or platform.

Argument Type Default Description
format str 'torchscript' Target format for the exported model, such as 'onnx', 'torchscript', 'tensorflow', or others, defining compatibility with various deployment environments.
imgsz int or tuple 640 Desired image size for the model input. Can be an integer for square images or a tuple (height, width) for specific dimensions.
keras bool False Enables export to Keras format for TensorFlow SavedModel, providing compatibility with TensorFlow serving and APIs.
optimize bool False Applies optimization for mobile devices when exporting to TorchScript, potentially reducing model size and improving performance.
half bool False Enables FP16 (half-precision) quantization, reducing model size and potentially speeding up inference on supported hardware.
int8 bool False Activates INT8 quantization, further compressing the model and speeding up inference with minimal accuracy loss, primarily for edge devices.
dynamic bool False Allows dynamic input sizes for ONNX and TensorRT exports, enhancing flexibility in handling varying image dimensions.
simplify bool False Simplifies the model graph for ONNX exports, potentially improving performance and compatibility.
opset int None Specifies the ONNX opset version for compatibility with different ONNX parsers and runtimes. If not set, uses the latest supported version.
workspace float 4.0 Sets the maximum workspace size in GB for TensorRT optimizations, balancing memory usage and performance.
nms bool False Adds Non-Maximum Suppression (NMS) to the CoreML export, essential for accurate and efficient detection post-processing.

It is crucial to thoughtfully configure these settings to ensure the exported model is optimized for the intended use case and functions effectively in the target environment.

Export Guide

Augmentation Settings

Augmentation techniques are essential for improving the robustness and performance of YOLO models by introducing variability into the training data, helping the model generalize better to unseen data. The following table outlines the purpose and effect of each augmentation argument:

Argument Type Default Range Description
hsv_h float 0.015 0.0 - 1.0 Adjusts the hue of the image by a fraction of the color wheel, introducing color variability. Helps the model generalize across different lighting conditions.
hsv_s float 0.7 0.0 - 1.0 Alters the saturation of the image by a fraction, affecting the intensity of colors. Useful for simulating different environmental conditions.
hsv_v float 0.4 0.0 - 1.0 Modifies the value (brightness) of the image by a fraction, helping the model to perform well under various lighting conditions.
degrees float 0.0 -180 - +180 Rotates the image randomly within the specified degree range, improving the model's ability to recognize objects at various orientations.
translate float 0.1 0.0 - 1.0 Translates the image horizontally and vertically by a fraction of the image size, aiding in learning to detect partially visible objects.
scale float 0.5 >=0.0 Scales the image by a gain factor, simulating objects at different distances from the camera.
shear float 0.0 -180 - +180 Shears the image by a specified degree, mimicking the effect of objects being viewed from different angles.
perspective float 0.0 0.0 - 0.001 Applies a random perspective transformation to the image, enhancing the model's ability to understand objects in 3D space.
flipud float 0.0 0.0 - 1.0 Flips the image upside down with the specified probability, increasing the data variability without affecting the object's characteristics.
fliplr float 0.5 0.0 - 1.0 Flips the image left to right with the specified probability, useful for learning symmetrical objects and increasing dataset diversity.
bgr float 0.0 0.0 - 1.0 Flips the image channels from RGB to BGR with the specified probability, useful for increasing robustness to incorrect channel ordering.
mosaic float 1.0 0.0 - 1.0 Combines four training images into one, simulating different scene compositions and object interactions. Highly effective for complex scene understanding.
mixup float 0.0 0.0 - 1.0 Blends two images and their labels, creating a composite image. Enhances the model's ability to generalize by introducing label noise and visual variability.
copy_paste float 0.0 0.0 - 1.0 Copies objects from one image and pastes them onto another, useful for increasing object instances and learning object occlusion.
auto_augment str randaugment - Automatically applies a predefined augmentation policy (randaugment, autoaugment, augmix), optimizing for classification tasks by diversifying the visual features.
erasing float 0.4 0.0 - 0.9 Randomly erases a portion of the image during classification training, encouraging the model to focus on less obvious features for recognition.
crop_fraction float 1.0 0.1 - 1.0 Crops the classification image to a fraction of its size to emphasize central features and adapt to object scales, reducing background distractions.

These settings can be adjusted to meet the specific requirements of the dataset and task at hand. Experimenting with different values can help find the optimal augmentation strategy that leads to the best model performance.

Logging, Checkpoints and Plotting Settings

Logging, checkpoints, plotting, and file management are important considerations when training a YOLO model.

  • Logging: It is often helpful to log various metrics and statistics during training to track the model's progress and diagnose any issues that may arise. This can be done using a logging library such as TensorBoard or by writing log messages to a file.
  • Checkpoints: It is a good practice to save checkpoints of the model at regular intervals during training. This allows you to resume training from a previous point if the training process is interrupted or if you want to experiment with different training configurations.
  • Plotting: Visualizing the model's performance and training progress can be helpful for understanding how the model is behaving and identifying potential issues. This can be done using a plotting library such as matplotlib or by generating plots using a logging library such as TensorBoard.
  • File management: Managing the various files generated during the training process, such as model checkpoints, log files, and plots, can be challenging. It is important to have a clear and organized file structure to keep track of these files and make it easy to access and analyze them as needed.

Effective logging, checkpointing, plotting, and file management can help you keep track of the model's progress and make it easier to debug and optimize the training process.

Argument Default Description
project 'runs' Specifies the root directory for saving training runs. Each run will be saved in a separate subdirectory within this directory.
name 'exp' Defines the name of the experiment. If not specified, YOLO automatically increments this name for each run, e.g., exp, exp2, etc., to avoid overwriting previous experiments.
exist_ok False Determines whether to overwrite an existing experiment directory if one with the same name already exists. Setting this to True allows overwriting, while False prevents it.
plots False Controls the generation and saving of training and validation plots. Set to True to create plots such as loss curves, precision-recall curves, and sample predictions. Useful for visually tracking model performance over time.
save False Enables the saving of training checkpoints and final model weights. Set to True to periodically save model states, allowing training to be resumed from these checkpoints or models to be deployed.

Created 2023-11-12, Updated 2024-06-10
Authors: glenn-jocher (17), fcakyon (2), Laughing-q (2), plashchynski (1), Burhan-Q (1), AyushExel (1), RizwanMunawar (1), tensorturtle (1)