---
description: Explore how to use the on-train, on-validation, on-pretrain, and on-predict callbacks in Ultralytics. Learn to update params, save models, and add integration callbacks.
keywords: Ultralytics, Callbacks, On-train, On-validation, On-pretrain, On-predict, Parameters update, Model saving, Integration callbacks
---
## on_pretrain_routine_start
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### ::: ultralytics.utils.callbacks.base.on_pretrain_routine_start
< br > < br >
## on_pretrain_routine_end
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### ::: ultralytics.utils.callbacks.base.on_pretrain_routine_end
< br > < br >
## on_train_start
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### ::: ultralytics.utils.callbacks.base.on_train_start
< br > < br >
## on_train_epoch_start
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### ::: ultralytics.utils.callbacks.base.on_train_epoch_start
< br > < br >
## on_train_batch_start
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### ::: ultralytics.utils.callbacks.base.on_train_batch_start
< br > < br >
## optimizer_step
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### ::: ultralytics.utils.callbacks.base.optimizer_step
< br > < br >
## on_before_zero_grad
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### ::: ultralytics.utils.callbacks.base.on_before_zero_grad
< br > < br >
## on_train_batch_end
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### ::: ultralytics.utils.callbacks.base.on_train_batch_end
< br > < br >
## on_train_epoch_end
---
### ::: ultralytics.utils.callbacks.base.on_train_epoch_end
< br > < br >
## on_fit_epoch_end
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### ::: ultralytics.utils.callbacks.base.on_fit_epoch_end
< br > < br >
## on_model_save
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### ::: ultralytics.utils.callbacks.base.on_model_save
< br > < br >
## on_train_end
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### ::: ultralytics.utils.callbacks.base.on_train_end
< br > < br >
## on_params_update
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### ::: ultralytics.utils.callbacks.base.on_params_update
< br > < br >
## teardown
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### ::: ultralytics.utils.callbacks.base.teardown
< br > < br >
## on_val_start
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### ::: ultralytics.utils.callbacks.base.on_val_start
< br > < br >
## on_val_batch_start
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### ::: ultralytics.utils.callbacks.base.on_val_batch_start
< br > < br >
## on_val_batch_end
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### ::: ultralytics.utils.callbacks.base.on_val_batch_end
< br > < br >
## on_val_end
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### ::: ultralytics.utils.callbacks.base.on_val_end
< br > < br >
## on_predict_start
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### ::: ultralytics.utils.callbacks.base.on_predict_start
< br > < br >
## on_predict_batch_start
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### ::: ultralytics.utils.callbacks.base.on_predict_batch_start
< br > < br >
## on_predict_batch_end
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### ::: ultralytics.utils.callbacks.base.on_predict_batch_end
< br > < br >
## on_predict_postprocess_end
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### ::: ultralytics.utils.callbacks.base.on_predict_postprocess_end
< br > < br >
## on_predict_end
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### ::: ultralytics.utils.callbacks.base.on_predict_end
< br > < br >
## on_export_start
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### ::: ultralytics.utils.callbacks.base.on_export_start
< br > < br >
## on_export_end
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### ::: ultralytics.utils.callbacks.base.on_export_end
< br > < br >
## get_default_callbacks
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### ::: ultralytics.utils.callbacks.base.get_default_callbacks
< br > < br >
## add_integration_callbacks
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### ::: ultralytics.utils.callbacks.base.add_integration_callbacks
< br > < br >
