YOLOv8-16bit/docs/reference/utils/callbacks/base.md

---
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
---

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

!!! note

    Full source code for this file is available at [https://github.com/ultralytics/ultralytics/blob/main/ultralytics/utils/callbacks/base.py](https://github.com/ultralytics/ultralytics/blob/main/ultralytics/utils/callbacks/base.py). Help us fix any issues you see by submitting a [Pull Request](https://docs.ultralytics.com/help/contributing/) 🛠️. Thank you 🙏!

---
## ::: ultralytics.utils.callbacks.base.on_pretrain_routine_start
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_pretrain_routine_end
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_train_start
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_train_epoch_start
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_train_batch_start
<br><br>

---
## ::: ultralytics.utils.callbacks.base.optimizer_step
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_before_zero_grad
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_train_batch_end
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_train_epoch_end
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_fit_epoch_end
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_model_save
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_train_end
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_params_update
<br><br>

---
## ::: ultralytics.utils.callbacks.base.teardown
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_val_start
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_val_batch_start
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_val_batch_end
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_val_end
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_predict_start
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_predict_batch_start
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_predict_batch_end
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_predict_postprocess_end
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_predict_end
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_export_start
<br><br>

---
## ::: ultralytics.utils.callbacks.base.on_export_end
<br><br>

---
## ::: ultralytics.utils.callbacks.base.get_default_callbacks
<br><br>

---
## ::: ultralytics.utils.callbacks.base.add_integration_callbacks
<br><br>