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description: Explore the detailed information on key Ultralytics callbacks such as on_pretrain_routine_end, on_model_save, on_train_start, and on_predict_start.
keywords: Ultralytics, callbacks, on_pretrain_routine_end, on_model_save, on_train_start, on_predict_start, hub, training
---

# Reference for `ultralytics/utils/callbacks/hub.py`

!!! Note

    This file is available at [https://github.com/ultralytics/ultralytics/blob/main/ultralytics/utils/callbacks/hub.py](https://github.com/ultralytics/ultralytics/blob/main/ultralytics/utils/callbacks/hub.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/callbacks/hub.py) 🛠️. Thank you 🙏!

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## ::: ultralytics.utils.callbacks.hub.on_pretrain_routine_end
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## ::: ultralytics.utils.callbacks.hub.on_fit_epoch_end
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## ::: ultralytics.utils.callbacks.hub.on_model_save
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## ::: ultralytics.utils.callbacks.hub.on_train_end
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## ::: ultralytics.utils.callbacks.hub.on_train_start
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## ::: ultralytics.utils.callbacks.hub.on_val_start
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## ::: ultralytics.utils.callbacks.hub.on_predict_start
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## ::: ultralytics.utils.callbacks.hub.on_export_start
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