---
title: utils.callbacks.hub API Reference
description: Explore detailed guides on Ultralytics callbacks, including pretrain, model save, train start/end, and more. Enhance your ML training workflows with ease.
keywords: Ultralytics, callbacks, pretrain, model save, train start, train end, validation, predict, export, training, machine learning
---

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

!!! success "Improvements"

    This page is sourced from [https://github.com/ultralytics/ultralytics/blob/main/ultralytics/utils/callbacks/hub.py](https://github.com/ultralytics/ultralytics/blob/main/ultralytics/utils/callbacks/hub.py). Have an improvement or example to add? Open a [Pull Request](https://docs.ultralytics.com/help/contributing) — thank you! 🙏

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## ::: ultralytics.utils.callbacks.hub.on_pretrain_routine_start

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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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