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description: Explore Ultralytics' versatile loss functions - VarifocalLoss, BboxLoss, v8DetectionLoss, v8PoseLoss. Improve your accuracy on YOLO implementations.
keywords: Ultralytics, Loss functions, VarifocalLoss, BboxLoss, v8DetectionLoss, v8PoseLoss, YOLO, Ultralytics Documentation
---

# Reference for `ultralytics/utils/loss.py`

!!! note

    This file is available at [https://github.com/ultralytics/ultralytics/blob/main/ultralytics/utils/loss.py](https://github.com/ultralytics/ultralytics/blob/main/ultralytics/utils/loss.py). If you spot a problem please help fix it by [contributing](https://docs.ultralytics.com/help/contributing/) a [Pull Request](https://github.com/ultralytics/ultralytics/edit/main/ultralytics/utils/loss.py) 🛠️. Thank you 🙏!

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## ::: ultralytics.utils.loss.VarifocalLoss
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## ::: ultralytics.utils.loss.FocalLoss
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## ::: ultralytics.utils.loss.BboxLoss
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## ::: ultralytics.utils.loss.KeypointLoss
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## ::: ultralytics.utils.loss.v8DetectionLoss
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## ::: ultralytics.utils.loss.v8SegmentationLoss
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## ::: ultralytics.utils.loss.v8PoseLoss
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## ::: ultralytics.utils.loss.v8ClassificationLoss
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