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