| 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 🙏! | |
| <br><br> | |
| ## ::: ultralytics.utils.callbacks.hub.on_pretrain_routine_end | |
| <br><br> | |
| ## ::: ultralytics.utils.callbacks.hub.on_fit_epoch_end | |
| <br><br> | |
| ## ::: ultralytics.utils.callbacks.hub.on_model_save | |
| <br><br> | |
| ## ::: ultralytics.utils.callbacks.hub.on_train_end | |
| <br><br> | |
| ## ::: ultralytics.utils.callbacks.hub.on_train_start | |
| <br><br> | |
| ## ::: ultralytics.utils.callbacks.hub.on_val_start | |
| <br><br> | |
| ## ::: ultralytics.utils.callbacks.hub.on_predict_start | |
| <br><br> | |
| ## ::: ultralytics.utils.callbacks.hub.on_export_start | |
| <br><br> | |